WINNIPEG, Manitoba, Jan 5 (Reuters) - The union representing more than 400 workers at Viterra's facilities in the Canadian province of Saskatchewan suspended plans for a strike on Friday to allow for a vote on the Rotterdam-based grain handler's latest contract offer.

The Grain and General Services Union said in the period leading up to the vote, employees will work to rule, meaning they will not take on tasks beyond their contractual and legal obligations.

Viterra is one of Canada's largest handlers of wheat, canola and other crops. The company is owned by commodity giant Glencore, the investment arm of the Canada Pension Plan and British Columbia Investment Management Corp.

Saskatchewan is Canada's biggest grain-growing province.

Viterra said in a statement that it is offering a four-year contract, with pay increases of 4.5% in the first year, 3.75% in the second year and 2.5% in each of the final two years.

The union vote will happen in the coming days and ballots will be counted on Jan. 19, the union said.

The two sides had met on Wednesday and Thursday with a federal mediator.

Bunge Ltd, a rival commodity firm, said last year that it would acquire Viterra, subject to regulatory approval in Canada and elsewhere. Canada is one of the world's largest wheat exporters. (Reporting by Rod Nickel in Winnipeg and Shivani Tanna in Bengaluru; Editing by Sriraj Kalluvila and Paul Simao)