Canadian aluminum producer Alcan has opened its books to mega-miners Rio Tinto and BHP Billiton in an attempt to fend off a $27 billion offer from American rival Alcoa, according to newspaper reports in The Sydney Morning Herald of Australia and the Globe and Mail of Canada.

BHP and Rio Tinto have declined to comment on these reports but some analysts say it would be no surprise for these firms to consider stopping an Alcan-Alcoa union that would create the world's biggest aluminum producer. Also, if either of the London-based miners had considered buying Montreal-based Alcan before, now could be their last chance.

However, Gavin Wendt of market analyst Fat Prophets believes neither BHP Billiton nor Rio Tinto would be able to extract the same kind of value from a takeover of Alcan that Alcoa could. "Any bid that BHP or Rio could mount, Alcoa could top, because there would be greater benefits flowing to them from a tie-up," he tells The Associated Press.