Calgary-based Agrium on Friday suffered a setback in its bid to take over rival CF Industries.

The bid could be thwarted by CF's separate campaign to take over a third company, Terra Industries of Sioux City, Iowa.

Terra shareholders voted Friday in favour of installing three CF-recommended directors to the Terra board. That increases the odds of Terra's board changing direction and recommending that their shareholders accept CF's $4.1-billion US offer.

Agrium's nearly $5-billion US offer for CF is conditional on it dropping its pursuit of Terra.

"I think that Agrium should simply take its marbles and go home. Agrium was a great company without CF and it's going to be a great company without CF in the future," said Mark Connelly, an analyst with Sterne Agee.