UPDATE 1-Union plots response to Viterra's contract move

(Updates, adds details from company)

By Allan Dowd

VANCOUVER, British Columbia, July 3 (Reuters) - Union officials on Thursday sparred with Viterra Inc. (VT.TO: Quote, Profile, Research) over a plan by Canada's largest grain handler to implement a contract offer that was already rejected by the workers.

Leaders of the Grain Services Union were deciding how to respond to the company's announcement late on Wednesday that it will institute the new wage system that ties wage increase to worker and company performance beginning July 7.

"We think we have offered a fantastic package, and we believe that we will have full attendance on Monday. It's business as usual," Mike Brooks, the company's chief information officer, said on Thursday.

Viterra, a name adopted by Saskatchewan Wheat Pool after its takeover last year of rival Agricore United, is in a contract dispute with some 200 unionized employees at its headquarters and as many as 750 grain elevator workers in Saskatchewan.

The workers voted last month to reject the company's last contract offer.

The union on Thursday disputed Viterra's claims that the offer would raise workers' wages by 27 percent over five years.

Viterra had not formally agreed to pay the higher wages to all the workers, aside from an initial signing bonus, and the offer included some money that employees were already scheduled to receive, the union said.