Agrium has, yet again, extended the deadline for its $4.1bn bid for CF Industries, keeping alive a three-way takeover fracas which stands to create the world's fourth-biggest fertilizer group.

Canada's Agrium, whose latest deadline was set to expire on Wednesday, said that investors now had until September 22 to tender their shares.

The extension came despite the number of investors who have withdrawn their backing for Agrium's bid since late June, when holders of 62% of CF stock accepted following a threat by Agrium to walk away unless it gained significant support.

As of Friday, holders of 10.5m CF shares, equivalent to 22% of the US group's market capitalisation.

'Fully committed'

Mike Wilson, the Agrium chief executive said that the group remained "fully committed" to acquiring CF.

"Despite the fact that CF continues to ignore a clear mandate to conclude a transaction, we will continue to press CF to execute a mutually beneficial merger agreement," he said.

CF has rejected Agrium's overtures in preference for its own plans to buy US nitrogen fertilizer specialist Terra Industries.

CF shares stood at 4.1% lower at $79.44 in afternoon trade in a weak New York market, 7.1% adrift of the value of Agrium's cash-and-shares bid.

Agrium stock was 5.6% down at $45.49.

Agrium and CF would, in theory, have a market capitalisation of about $11.7bn once merged, making it the world's fourth biggest listed fertilizer group behind PotashCorp, Mosaic and Israel Chemical.