BHP Billiton scrapped its $39 billion bid for Canada's Potash Corp and bowed to calls from investors to return cash, a move that came days after regulators blocked the year's biggest takeover deal.

BHP, conceding defeat for the third straight time on a major proposed merger or acquisition, signalled with its revived $4.2 billion share buyback that it had limited opportunities for other big buys.

The world's largest miner's shareholders are eager to hear what further growth prospects the company will chase with its cash pile when BHP chief executive Marius Kloppers fronts the group's annual meeting in Australia today.

'Certainly the best investment is probably in themselves at the moment,' said Brendan James, a partner at BHP shareholder Perennial Growth, referring to the prospect of a bigger buyback.

Canada blocked BHP's hostile bid for the world's largest fertiliser maker on November 3 and gave BHP a month to prove the takeover would benefit Canada.

'Unfortunately, despite having received all required antitrust clearances for the offer, we have not been able to obtain clearance under the Investment Canada Act and have accordingly decided to withdraw the offer,' Kloppers said.

It will be tough for the world's largest miner to chase other major buys, given its size and dominance in most of its markets. Analysts said BHP may look at takeovers in the petroleum sector since it is only a mid-sized player in that industry and would be less likely to run into competition hurdles.