CALGARY - Canadian fertilizer giant Agrium Inc. is in danger of seeing longtime target CF Industries Holdings Inc. slip away, now that the U.S. company has won important support for a US$4.7-billion takeover of its own.

The offer by Agrium (TSX:AGU), which has been rebuffed repeatedly in its attempts to buy Deerfield, Ill.-based CF for more than a year, is contingent on CF giving up its pursuit of Iowa-based fertilizer company Terra Industries Inc.

However Terra ruled Wednesday that CF's latest overture for the company was superior to a friendly deal with Norway's Yara International worth US$4.1 billion, leaving Agrium - which has vowed not to overpay for CF - in a tough spot.

"I think their choice is simple. They have to make a huge bid for CF in order to make CF's board think twice before getting into the Terra deal," said Edlain Rodriguez, an analyst with Broadpoint AmTech in New York.

Agrium spokesman spokesman Richard Downey said the news Wednesday didn't change anything.

"What will matter is what Yara does with regard to whether they decide to increase their bid or not. That's probably the key determining factor," Downey said.

Calgary-based Agrium's offer of US$45 in cash plus one of its shares for each CF share values the U.S. company at nearly US$5.5-billion. That offer is on the table until March 22, unless it's withdrawn, extended or modified.

"I would think CF's shareholders would rather receive a juicy premium from Agrium, but I don't know if they have that choice," said Rodriguez.

CF has a so-called "poison pill" provision in place, which makes it difficult and costly for any unwelcome acquirer to complete a transaction without the CF board's approval.

Agrium has pressed CF to drop its poison pill and let its shareholders have their say. Agrium also has plans to try to have its own nominees installed on CF's board of directors at the target company's annual general meeting this spring.

But CF also faces a potential hurdle from Yara, which has five business days to meet or beat CF's offer of US$4.7 billion in cash and stock.

However, CF issued a statement Wednesday proclaiming it will prevail.

"We believe that Terra is worth more to CF Industries than to any other acquirer, given the strategic benefits of the transaction, including synergies, which only CF Industries can achieve," said Stephen Wilson, chairman, president and chief executive officer of CF.

"Any offer from Yara must be heavily discounted for the substantial risks and length of time associated with closing."

Terra shares rose two per cent Wednesday afternoon on the New York Stock Exchange to US$46.80, while CF stock gained 1.7 per cent to US$102.30.

Agrium shares rose 62 cents to US$68.37 in New York and 61 cents to US$70.11 in Toronto.