PotashCorp Board of Directors Rejects BHP Billiton's Unsolicited Offer

Deems US$130 per Share Offer Wholly Inadequate

SASKATOON, Canada, August 23, 2010 - Potash Corporation of Saskatchewan Inc. ("PotashCorp") today
announced that its Board of Directors, after careful consideration with the
assistance of its independent financial and legal advisors, voted unanimously
to reject the unsolicited offer by BHP Billiton Development 2 (Canada)
Limited, an indirect wholly-owned subsidiary of BHP Billiton Plc
(LSE:BLT/JSE:BIL/NYSE:BBL) ("BHP Billiton"), to acquire all of the
outstanding shares of PotashCorp for US$130 per share in cash. The Board
unanimously recommends that PotashCorp shareholders reject the BHP Billiton
offer and not tender their shares.

The basis for the PotashCorp Board's recommendation with
respect to the BHP Billiton offer is set forth in PotashCorp's Directors'
Circular and Schedule 14D-9, which were filed today with the Canadian and
U.S. securities regulatory authorities and are being mailed to shareholders.

"The PotashCorp Board of Directors is unanimous in its belief
that the BHP Billiton offer substantially undervalues PotashCorp and fails to
reflect both the value of our premier position in a strategically vital
industry and our unparalleled future growth prospects," said PotashCorp
President and Chief Executive Officer Bill Doyle. "The Board thoroughly
reviewed the formal offer documents in connection with BHP Billiton's
unsolicited offer and concluded that the offer is wholly inadequate and is
not in the best interests of the Company, its shareholders or other
stakeholders. We strongly urge shareholders to reject BHP Billiton's
opportunistic offer and not tender their shares."

The reasons for the PotashCorp Board's recommendation to
reject BHP Billiton's offer are detailed in the Directors' Circular and the
Schedule 14D-9, and include, among other things, the Board's belief that:

- PotashCorp is a uniquely valuable asset.

The PotashCorp Board believes that the Company is uniquely
positioned as the premier global potash producer with unparalleled assets in
an industry where supply is characterized by substantial barriers to entry,
few producers, low government ownership and no known product substitutes. At
the same time, demand-side drivers are strong and irrefutable. The Company
believes that PotashCorp is uniquely positioned to benefit from these
dynamics and that the BHP Billiton offer fails to adequately compensate
Shareholders for this strategic position and scarcity value. In addition,
PotashCorp believes that the BHP Billiton offer does not reflect PotashCorp's
substantial recent and ongoing investments to increase capacity, the value of
PotashCorp's strategic equity investments in China, Chile, Jordan and Israel
and PotashCorp's unmatched ability to meet the needs of North American
customers and growing offshore potash markets.

- The BHP Billiton offer fails to reflect PotashCorp's
prospects for continued growth and shareholder value creation.

PotashCorp is poised to deliver strong earnings growth as
agricultural fundamentals continue to strengthen and demand for its products
rises. The Company believes that the potash market is approaching an
inflection point, characterized by increasing global demand for potash and
higher prices. Along with its significant portfolio of high-quality, low-cost
assets in Canada, its strategic investments in other potash businesses
uniquely position PotashCorp to capture a disproportionate share of demand
and earnings growth in the coming years. PotashCorp's Board and management
team are highly confident that the Company can continue its strong track
record of success, realize upon the growth opportunities available to it in
the current market environment, and deliver more value to shareholders than
the inadequate BHP Billiton offer.

- The BHP Billiton offer is timed to deprive shareholders of full value.

The PotashCorp Board believes that the timing of the BHP
Billiton offer is highly opportunistic, that it represents an ill-disguised
attempt to exploit an anomaly in the equity market valuation of PotashCorp
and that BHP Billiton is opportunistically attempting to transfer the upside
value in PotashCorp to its own shareholders at the expense of PotashCorp
shareholders. The Company believes that BHP intentionally launched the BHP
Billiton offer just as the fertilizer industry is emerging from an
unprecedented demand decline associated with the global economic downturn, in
order to seize the value that PotashCorp is poised to create. PotashCorp is
uniquely positioned to capitalize on growth opportunities present in its
industry. Given the demand growth and margin potential anticipated in the
months and years ahead, the PotashCorp Board believes that the continued
execution of PotashCorp's strategic plan will deliver substantially more
value to shareholders than the BHP Billiton offer.

- The BHP Billiton offer represents a wholly inadequate premium for
control.

At US$130 per share, BHP Billiton is proposing a premium of
only 16% over PotashCorp's closing stock price on August 16, 2010, the day
before PotashCorp's announcement of BHP Billiton's unsolicited proposal. This
low premium does not, in PotashCorp's view, reflect the strategic importance,
scarcity value or quality of PotashCorp's assets, nor the unique investment
opportunity PotashCorp affords to BHP Billiton or any other potential
acquiror. The premium being offered is substantially inferior to control
premiums paid for other marquee Canadian-based resource companies.

- The consideration offered under the BHP Billiton offer
represents a 13.1% discount to the closing price of PotashCorp common shares
on August 20, 2010, the last trading day prior to filing the Directors'
Circular and Schedule 14D-9.

Since the announcement of BHP Billiton's unsolicited approach
on August 17, 2010, the PotashCorp common shares have consistently traded
above the offer price. PotashCorp believes that the performance of the common
shares during this period is a strong indicator that the market believes that
the BHP Billiton offer undervalues the common shares.

- PotashCorp's financial advisors have each provided a written
opinion to the Board that the consideration being offered pursuant to the BHP
Billiton offer was, as of the date of such opinions, inadequate, from a
financial point of view, to shareholders (other than BHP Billiton and any of
its affiliates).

The PotashCorp Board has received written opinions dated
August 22, 2010 from each of BofA Merrill Lynch, Goldman, Sachs & Co. and RBC
Capital Markets to the effect that, as of such date and based upon and
subject to the assumptions, limitations and qualifications stated in their
respective opinions, the consideration offered by BHP Billiton under the BHP
Billiton offer was inadequate, from a financial point of view, to
shareholders (other than BHP Billiton and any of its affiliates). Copies of
the opinions are set forth in PotashCorp's Directors' Circular and Schedule
14D-9. [1]

- Superior offers or other alternatives are expected to emerge.

Since August 12, 2010, the date that BHP Billiton first
approached PotashCorp in respect of the BHP Billiton offer, the PotashCorp
Board, together with PotashCorp's management team and financial and legal
advisors, have been working to evaluate a range of strategic alternatives
that may enhance shareholder value. PotashCorp has been approached by, and
has initiated contact with, a number of third parties who have expressed an
interest in considering alternative transactions. Discussions are being
pursued with several of these third parties in order to generate value
enhancing alternatives.

- The BHP Billiton offer is coercive and not a "Permitted Bid"
under PotashCorp's Shareholder Rights Plan.

PotashCorp's Shareholder Rights Plan enables potential
acquirors to make a "Permitted Bid" without the approval of the PotashCorp
Board. Among other things, a Permitted Bid provides the PotashCorp Board with
additional time for the exploration, development and pursuit of alternatives
that could enhance shareholder value. A Permitted Bid also makes it more
likely that holders of common shares have sufficient time to consider all
appropriate alternatives and do not feel compelled to accept a bid for fear
that other shareholders would tender and they would remain as minority
shareholders in a corporation with a new controlling shareholder, and with
significantly less liquidity and the absence of any takeover premium. BHP
Billiton was able to make a Permitted Bid as the Shareholder Rights Plan was
adopted and announced, and a copy publicly filed, prior to the BHP Billiton
offer being mailed, but BHP Billiton chose not to make a Permitted Bid. On
August 22, 2010, the PotashCorp Board decided to defer the "separation time"
of the rights under the Shareholder Rights Plan.

- The BHP Billiton offer is highly conditional.

The PotashCorp Board is concerned about the fact that the BHP
Billiton offer is highly conditional, to the benefit of BHP Billiton. There
are conditions which are not subject to a materiality threshold or other
objective criteria but rather provide BHP Billiton with a broad range of
grounds upon which it may decline to proceed with the BHP Billiton offer,
with the result that the tendering of common shares to the BHP Billiton offer
could, under certain circumstances, effectively constitute little more than
the grant of an option to BHP Billiton to acquire common shares.

PotashCorp shareholders are urged not to tender into the BHP
Billiton offer and to carefully review the Directors' Circular and the
Schedule 14D-9 in their entirety. These documents will be available free of
charge on SEDAR at www.sedar.com, on the SEC's website at
www.sec.gov and on PotashCorp's website at www.potashcorp.com.

BofA Merrill Lynch, Goldman, Sachs & Co. and RBC Capital
Markets are acting as financial advisors to PotashCorp and Jones Day and
Stikeman Elliott LLP are acting as its legal advisors.

About PotashCorp

Potash Corporation of Saskatchewan Inc. is the world's largest
fertilizer enterprise by capacity producing the three primary plant nutrients
and a leading supplier to three distinct market categories: agriculture, with
the largest capacity in the world in potash, third largest in each of
nitrogen and phosphate; animal nutrition, with the world's largest capacity
in phosphate feed ingredients; and industrial chemicals, as the largest
global producer of industrial nitrogen products and the world's largest
capacity for production of purified industrial phosphoric acid. PotashCorp's
common shares are listed on the Toronto Stock Exchange and the New York Stock
Exchange.

This release contains forward-looking statements or forward-looking
information (forward-looking statements). These statements are based on
certain factors and assumptions including foreign exchange rates, expected
growth, results of operations, performance, business prospects, evaluations
and opportunities and effective income tax rates. While the company considers
these factors and assumptions to be reasonable based on information currently
available, they may prove to be incorrect. Several factors could cause actual
results to differ materially from those expressed in the forward-looking
statements, including, but not limited to: future actions taken by BHP
Billiton in connection with its unsolicited offer; fluctuations in supply and
demand in fertilizer, sulfur, transportation and petrochemical markets;
changes in competitive pressures, including pricing pressures; the recent
global financial crisis and conditions and changes in credit markets; the
results of sales contract negotiations with China and India; timing and
amount of capital expenditures; risks associated with natural gas and other
hedging activities; changes in capital markets and corresponding effects on
the company's investments; changes in currency and exchange rates; unexpected
geological or environmental conditions, including water inflow; strikes and
other forms of work stoppage or slowdowns; changes in and the effects of,
government policy and regulations; and earnings, exchange rates and the
decisions of taxing authorities, all of which could affect our effective tax
rates. Additional risks and uncertainties can be found in our Form 10-K for
the fiscal year ended December 31, 2009 under captions "Forward-Looking
Statements" and "Item 1A - Risk Factors" and in our other filings with the US
Securities and Exchange Commission and Canadian provincial securities
commissions. Forward-looking statements are given only as at the date of this
release and the company disclaims any obligation to update or revise the
forward-looking statements, whether as a result of new information, future
events or otherwise, except as required by law.

Important Information

This press release is neither an offer to purchase nor the solicitation
of an offer to sell any securities. On August 23, 2010, PotashCorp filed a
solicitation/recommendation statement on Schedule 14D-9 with the Securities
and Exchange Commission (the "SEC") with respect to the offer to purchase
commenced by BHP Billiton Development 2 (Canada) Limited, a wholly-owned
subsidiary of BHP Billiton Plc. Investors and security holders of PotashCorp
are urged to read the solicitation/recommendation statement and any other
relevant documents filed with the SEC, because they contain important
information.

Investors and security holders may obtain a free copy of the
solicitation/recommendation statement and other documents that PotashCorp
files with the SEC through the website maintained by the SEC at
www.sec.gov and through the website maintained by PotashCorp at
www.potashcorp.com. In addition, the solicitation/recommendation
statement and other documents filed by PotashCorp with the SEC may be
obtained from PotashCorp free of charge by directing a request to Potash
Corporation of Saskatchewan Inc., 122 - 1st Avenue South, Suite 500,
Saskatoon, Saskatchewan, Canada S7K 7G3, +1-306-933-8500.

———————————

[1] Shareholders are urged to read each opinion carefully and in its
entirety for a description of the procedures followed, matters considered and
limitations on the review undertaken. The opinions were provided for the
information and assistance of the PotashCorp Board in connection with its
consideration of the BHP Billiton offer. The opinions do not constitute a
recommendation to shareholders as to whether they should tender their common
shares to the BHP Billiton offer.

For further information, please contact:

    Investors

    Denita Stann
    Senior Director, Investor Relations
    Phone: +1-847-849-4277
    Email: ir@potashcorp.com

    In Canada:
    Georgeson
    (866)425-8527

    In the U.S. (and elsewhere outside of Canada):
    Innisfree M&A Incorporated
    In the U.S.: (877)717-3923
    In the E.U.: 00-800-7710-9970
    Banks, Brokers and from Other Locations: +1-212-750-5833

    Media

    Bill Johnson
    Director, Public Affairs
    Phone: +1-306-933-8849
    Email: pr@potashcorp.com

    Eric Brielmann / Jamie Moser / Andrew Siegel
    Joele Frank, Wilkinson Brimmer Katcher
    Phone: +1-212-355-4449

Web Site: www.potashcorp.com

Media: Bill Johnson, Director, Public Affairs, Phone: +1-306-933-8849, Email: pr at potashcorp.com; Eric Brielmann / Jamie Moser / Andrew Siegel, Joele Frank, Wilkinson Brimmer Katcher, Phone: +1-212-355-4449