Canadian Auto Workers Local 222 president Chris Buckley spoke with reporters on Wednesday morning. (CBC)

Union members set up a blockade outside General Motors' Canadian headquarters on Wednesday, a day after the automaker announced it was halting production at four factories across North America.

"Nobody is going into GM’s head office as long as we're standing here today," Canadian Auto Workers Local 222 president Chris Buckley told CBC News, noting that workers have been allowed to cross the blockade on foot, but not with their vehicles.

GM CEO Rick Wagoner was to meet with CAW president Buzz Hargrove on Friday, but Buckley said the blockade will remain in place. He said the union wants GM to reverse its decision, which will leave about 2,600 employees out of work.

"This decision will have an absolutely devastating impact, not only on 2,600 of my members, but throughout this community, throughout our province."

The Oshawa plant, which produces the Chevrolet Silverado and the GMC Sierra, is expected to close in 2009, GM CEO Rick Wagoner said Tuesday during a news conference in Wilmington, Del., prior to the company's annual meeting.

Three other GM plants that assemble pickups or sport utility vehicles are also scheduled to be closed — in Janesville, Wis., Moraine, Ohio, and Toluca, Mexico.

Closure an 'illegal' betrayal: union

The CAW has promised an all-out fight against what it called an "illegal" betrayal. In May, the CAW reached an agreement with GM to postpone a 900-worker layoff at the Oshawa truck plant until September 2009.

As part of that agreement, GM also promised that the Oshawa plant would be employed to work on the next generation of light-duty pickup trucks, Buckley said Tuesday.

"I find it very hard to believe in the last two weeks things have gotten any worse than they were when they committed that."

He said that if the company refuses to manufacture pickup trucks at the plant, it must replace them with another vehicle in order to keep workers on the job.

GM, however, has said it does not plan to allocate any new products to the four plants slated for closure.

Wagoner said Tuesday that higher gasoline prices are rapidly changing the auto industry sales mix, as consumers shift away from large trucks and SUVs.

GM's U.S. sales of trucks were down 39 per cent in May, compared with the same month last year. GM's overall sales of all vehicles were down 30 per cent year-over-year.

"It doesn't make sense to have a plant producing vehicles that nobody is going to be buying," said David Paterson, GM Canada's vice-president of corporate and environmental affairs.

Paterson pointed out that the company currently has three shifts building Chevrolet Impalas at the Oshawa car plant, and there are plans to bring back about 600 people from layoff to begin startup work on the new Camaro, which will go into production at the end of this year.

Buckley said he understands the impact rising fuel costs and a strong Canadian dollar have had on the auto industry, but pointed out that the company intends to continue making pickup trucks in Mexico and the U.S.

Union activists will continue their blockade "as long as it takes," Buckley said, although there has been no directive for workers to walk off the job.

“I am encouraging all of my members to stay on the job and continue to build the best trucks and cars in the industry.”