Strikers at two Vale Inco operations in Ontario will vote to reject the company's latest offer, an official with their union, the United Steelworkers, predicted Wednesday.

More than 3,000 Steelworkers in Sudbury and 130 in Port Colborne will vote Thursday and Friday on the offer Vale Inco made Sunday in an effort to settle their eight-month strike.

Workers picket the Vale Inco smelter complex in Copper Cliff, near Sudbury, Ont. The strike started in July. (Gino Donato/Canadian Press)

Wayne Fraser, the director of Steelworkers District 6, said he is confident they will reject the offer, as the union recommends.

Fraser said that otherwise, there would be no guarantees about who goes back to work, when they go back or where they will be working. The offer is the second of two that Vale Inco gave the union during talks with a mediator.

A Vale Inco spokesman says a vote to accept will mean the union and the company will have to negotiate and agree on a process by which members can return to work.

The workers have been on strike for eight months.

The strike started after Vale proposed reducing a bonus tied to the price of nickel.

Workers also opposed the company's plan to exempt new employees from its defined-benefit pension plan, which guarantees the pension amount retirees get, to a defined-contribution plan, which bases retirement benefits on investment returns.

The workers have been without a contract since it expired when the strike began on July 13, 2009.

With files from The Canadian Press