CF Industries Holdings Inc. (CF) said Monday that fertilizer rival Agrium Inc. (AGU) could afford to price its hostile takeover bid at $100 a share, reiterating its rejection of a lower offer.

CF's board has called on shareholders to reject Agrium's offer of $31.70 in cash and 1.7866 of its own shares for each CF share, or $72 in cash. The offer, which Agrium is taking directly to CF shareholders, was valued at $67.96 based on Friday's closing prices.

The U.S. fertilizer company railed against the offer from the larger Canadian company, criticizing its integration efforts in previous deals and claiming it was trying to buy CF on the cheap at the bottom of the market.

On a conference call, CF executives said their advisers suggested Agrium could afford to pay $100 a share and still keep a deal accretive, and also criticized the "vagueness" of its suitor's synergy targets.

Steve Wilson, CF's chief executive, said on the call that industry pricing has improved since the final quarter of 2008 after a slump that wiped billions of dollars from sector valuations.

CF also sweetened its all-stock bid for Terra Industries Inc. (TRA) to $3.07 billion.

-By Doug Cameron, Dow Jones Newswires; 312-750-4135; doug.cameron@dowjones.com