Saskatchewan Premier Brad Wall said Friday that Manitoba's premier has joined him in opposing the hostile takeover of Potash Corporation of Saskatchewan by Australian mining giant BHP Billiton.

Wall told reporters in Toronto that Manitoba Premier Greg Selinger is onside.

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Wall announces his opposition to the PotashCorp takeover on Oct. 21 in Regina. ((CBC))

"He, too, wants us to balance a welcoming investment climate — to be open to foreign direct investment, but to be concerned about the strategic nature of the resources that we have," Wall said. 

Wall emphasized that natural resources belong to the provinces and that the premiers want to make sure their interests are represented in Ottawa when foreign companies seek to invest in Canada.

Alberta Premier Ed Stelmach joined opposition to the deal on Wednesday, and Wall said on Thursday that Quebec's Jean Charest had offered his support to Saskatchewan's position.

Wall said the other premiers agree with him that BHP ownership of PotashCorp wouldn't be of net benefit to Canadians.

He said his stance doesn't mean he's against foreign investment, but said the strategic importance of Saskatchewan's potash — about half of the world's reserves of the mineral used in fertilizer — makes this deal of special significance.

Wall first came out against the deal Oct. 21, saying it could cost the provincial treasury billions of dollars in lost royalties and taxes over a decade.

Also Friday, federal Industry Minister Tony Clement said he won't extend Wednesday's deadline for deciding whether to disallow the takeover.

Ottawa is considering whether the proposed deal, valued at $38.6 billion US, or $130 a share, meets the requirements of the Investment Canada Act by providing net benefits to Canada.

Spoken with 15 bidders

Meanwhile, PotashCorp disclosed in a regulatory filing that it has spoken to 15 "financial and state-sponsored potential bidders or investors" about making a competing bid for the company.

"The PotashCorp board believes that there is a real and substantial probability that alternatives to the BHP offer will emerge that will increase shareholder choice and enhance shareholder value," the company said in a filing with Saskatchewan's securities regulator.

Earlier, federal New Democrat Leader Jack Layton repeated his call for a change to the act to make the review process of foreign takeovers transparent.

The review is held behind closed doors, and Layton called on Prime Minister Stephen Harper to support an NDP motion to be tabled next week that calls for the foreign investment review process to be open.

"If the government decides to give BHP the green light here, nobody is going to know why," Layton said at a news conference. "They don't have to tell us, and that's wrong."

Potash shares closed up $1.50, or one per cent, at $147.50 on the Toronto Stock Exchange Friday.

With files from The Canadian Press