Dozens of locked out steelworkers picketed a Hamilton mill on Monday, after U.S. Steel locked hundreds of workers out amid a contract dispute.

Members of the United Steelworkers union set up picket lines after the company locked the doors of the former Stelco steel mine on Sunday, barring 900 employees from work.

U.S. Steel is demanding a vote on a "final" contract offer that demands several concessions from the workers, including broad cuts to the pension plan. It says the concessions are needed for the plant to be competitive.

The Pittsburgh company demands that the offer it made Nov. 4, delivered to the union by a provincial mediator, be put to a vote.

Part of the contract would see the existing pension plan closed to new employees and be replaced by a defined contribution retirement savings plan. It also wants an end to the indexing of pension payments for the plant's 9,000 retired workers.

Rolf Gerstenberger, the head of Steelworkers Local 1005, says it is absurd to even consider voting on a contract that would leave retired workers out in the cold.

"Do they want to just openly declare that Canadians don't deserve a pension plan anymore? Is that the official position?" Gerstenberger asked CTV News. "We also have a Canada Pension Plan, which is a defined benefit plan. Their logic goes that everybody's retirement is going to depend on how the market does. If it doesn't do well, too bad. You can starve."

The current lockout comes as the steel industry's goes through hard times. U.S. Steel was forced to fire hundreds of employees two years ago, including 177 workers in two Ontario plants – in Hamilton and Nanitoke – it had purchased in 2007.

Workers at the Nanticoke plant resolved an eight-month lockout in April.

Last month the company stopped producing raw steel at the Hamilton plant based on weak demand, redeploying its employees to other functions within the plant.

U.S. Steel is in an extended court battle with Ottawa over promises it made when it purchased the Stelco plant for more than $1 billion.

With a report from CTV Toronto's John Musselman and files from The Canadian Press