The Canadian Auto Workers union says it's not surprised General Motors is going to court to try to end the blockade of its Canadian headquarters in Oshawa, but union officials have no plans to back down.

Police arrived at the protest on Tuesday morning when the workers refused to let company executives into their offices.

GM is expected to seek an injunction and force workers at its Oshawa plant to end their roadblock.

The blockade has been in place since last Wednesday morning.

Local union president Chris Buckley said he will see how aggressively the company pursues its battle before the union comes up with its next phase of its demonstration.

Buckley wouldn't say whether the union would consider ignoring a court order to end the blockade.

The workers set up the roadblock at GM's Canadian headquarters to protest the pending closure at the truck plant, which is slated for the fall of 2009. The closure will put about 2,600 employees out of work.

The announcement came just weeks after the company and the Canadian Auto Workers union reached a tentative agreement. GM has said rising fuel costs have forced them to downsize production on some of their gas-guzzling vehicles.

Buckley says workers will step up their action on Thursday as the union is planning a massive rally. Posters are going up throughout the Durham region in hopes of attracting 10,000 supporters to the rally.

Buckley wouldn't say what other measures the union might be planning to put further pressure on GM.

"At this time I'll keep that to myself but we are not going to give up our fight to save the jobs of 2,600 of our members," he said.

"This is about our members, their families and all of our communities and we're not going to stop."

Buckley says the union hasn't ruled out a wildcat strike.

CAW president Buzz Hargrove, however, said workers don't plan to stir up trouble.

"We have a rally on Thursday, and our local people have said they're going to follow the law,'' he said in Toronto after a CAW meeting. "They're not going to challenge the law, so if there's an injunction I assume that would mean they would live by the injunction.''

Hargrove admitted prospects for the workers appear bleak as the union can't find any precedent where a company was forced to invest or keep a plant open once they made a decision to close it down.

Hargrove said taking the issue to Parliament may be the best chance to save the Oshawa facility.

"If we could get a resolution saying General Motors must live by the principles of the Canada-U.S. Auto Pact, then GM can't do that unless they keep the truck plant open,'' he said.

"One thing about General Motors and the companies is they don't like to violate the law. If the politicians are joining us on the issue here, I think it can make a difference. It may not -- maybe GM will tell everybody to go to hell, who knows? There's an arrogance out there today that's unprecedented in my lifetime.''

With files from The Canadian Press