TORONTO - A temporary shutdown of General Motors Corp.'s truck plant in Oshawa, Ont., announced Monday has dealt the latest blow to Canadian autoworkers as the industry grapples with declining sales numbers spurred by higher fuel prices.

About 1,000 employees will be affected by the closure, which will temporarily lay off the workers for eight separate weeks of down time, GM spokeswoman Patty Faith said.

The temporary layoffs will begin in July after a normal two-week annual shutdown to adjust operations for the model-year changeover.

After that, seven more weeks of down time will occur at unspecified points between July and the end of the year, Faith said.

Canadian Auto Workers union president Buzz Hargrove said Oshawa is scheduled to resume regular production in January and the temporary closure was considered "additional time off which will be covered by EI (unemployment insurance).''

He added that GM still plans to close the Oshawa truck facility in the fall of 2009, though the union intends to "try and find every way we can to change their mind or stop them.''

Industry watcher Dennis DesRosiers said the latest GM announcement was purely market-driven, and didn't surprise him.

He noted that GM truck production has declined 70 per cent this year in Canada, while it's down 40 per cent in the United States.

"I don't think General Motors is trying to play to anybody here, I think they're playing to one thing only -- and that's the market. They're not playing politics here,'' he said.

Earlier Monday, the CAW issued new data which claims that during the first four months of the year Canada's auto trade deficit almost doubled to $3.7 billion, caused by a "sharp decline'' in auto exports to the United States, and higher imports from overseas.

Exports of finished vehicles dropped 25 per cent, the report said.

The union estimated that Canada's auto trade defect could climb to more than $10 billion if the current trend holds steady. Last year the defect was just $6.6 billion.

Hargrove has been pushing Ottawa to regulate automotive imports and make arrangements with foreign governments to import Canadian parts and vehicles. He said those actions would help turnaround the struggling industry.