Agrium, the Canadian fertilizer giant, urged board members at CF Industries to run up the white flag after a last-minute rush of support from the group's shareholders for a $4bn bid.

Mike Wilson, the Agrium chief executive, said that investors had sent a "resounding message" to the CF board after holders of 62% of the US group's stock tendered to the offer ahead of the June 22 deadline.

Holders of just 3.1% of CF shares had tendered three weeks ago, the last time Agrium revealed acceptance levels.

"These are extraordinarily strong results," Mr Wilson said.

"We urge CF's board to respect this clear message from its stockholders."

CF reaction

However, the CF board restated its opposition to the CF offer as too low.

"Contrary to Agrium's assertions, the tender offer results do not change the facts that Agrium's offer substantially undervalues CF Industries," Stephen Wilson, the CF chairman and chief executive officer said.

He added that the offer "has significant regulatory issues".

'Expeditious' execution

Law in the US state of Delaware, where CF is incorporated, decrees that a bid can only go through with the support of the target company's directors. CF's board has until now rejected Agrium's bid as "substantially" too low.

Agrium was prepared to meet CF "immediately" and "to expeditiously execute a fully-financed, binding merger agreement", Mr Wilson added.

"As we have previously stated, a combined Agrium-CF would be a terrific company. We will continue to press forward to complete this compelling combination."

Agrium added that it would extend the expiry date for the offer until July 22, giving further investors the chance to tender.

Market reaction

On the New York stock market, CF shares jumped 4.5% to $72.45 in morning deals.

Agrium shares added 3.7% to $40.31, valuing its cash-and-shares bid at $80.31 per CF share.