Giant mining firm BHP Billiton Ltd (ASX: BHP) revealed on Tuesday that it has extended the period of its takeover bid for Canadian fertiliser producer Potash Corporation of Saskatchewan for another 30 days following receipt of notice from the Canadian Competition Bureau.

The company said that it has been issued a Supplementary Information Request by the Canadian regulatory body, prompting for the extension of its $US130 per share offer until November this year as BHP expressed optimism that "the offer will receive all requisite regulatory approvals in due course."

Meanwhile, Canadian Prime Minister Stephen Harper declared a day earlier that the proposals to buyout the world's largest maker of fertiliser would be closely scrutinised by the country's competition bureau in order to ensure that the looming foreign takeovers would result to considerable net benefit for Canada.

Following the rejection of its original bid, BHP Billiton resorted to its billion-dollar hostile takeover proposal for Potash Corp as reports circulated that a rival bid could be in making from Chinese companies backed by Beijing.

Mr Harper said that the state government of Saskatchewan has transmitted its concerns to the federal government, apparently alarmed of the prospect that foreign firms would end up running a major company in the state.

The Canadian leader stressed that foreign takeovers are not automatically approved, underscoring the fact that the federal leadership could block any corporate bid that are deemed inimical to the country's interest.

Mr Harper said that it is not the policy of the Canadian government "to give a blank check to foreign takeovers," as he asserted that any takeover proposal must go through the requirements of the Canada Investment Act that was enacted in 1989.

The Canadian prime minister, however, is known to lean towards free trade as his conservative government recently allowed Chinese investors to take part in the country's oil and sand industry.

Yet this time, the Canadian government is caught up with advancing its political agenda while protecting at the same time the interest of its regional industries and in the case of Potash Corp, analysts said that Mr Harper must address Saskatchewan's concern that bids coming from both BHP and Chinese firms would lead to great disadvantages for the region.

Potash Corp has been one of the province's biggest revenue-contributing companies and the regional government fears that giving up the firm to foreign companies would eventually lead to lower potash prices and eventually reduce the region's financial benefits.