Potash Corporation in Canada has filed a law suit to try to stop a $US40 billion hostile takeover by BHP Billiton.
The world's largest fertiliser company says BHP's bid is built on false and misleading statements, designed to coerce shareholders into selling their shares in Potash.
It also accuses BHP of trying to drive down the price of Potash's share price to boost its chances of buying them.
BHP's offer for Potash expires on 18 November.
