* Workers at GM Canada's car seat supplier Lear on strike
* Union says GM Oshawa seat supply to last 4-5 hours
* Workers at GM engine part supplier Wescast also on strike
By Susan Taylor
TORONTO, Oct 29 (Reuters) - Production at General Motors Co's Oshawa, Ontario, plant could shut down Monday as a strike at Lear Corp cut off supplies of seats used in vehicles assembled there, the Canadian Auto Workers (CAW) union said on Monday.
About 400 workers at Lear's plant in Whitby, Ontario, went on strike on Sunday after talks broke down over company requests for contract concessions, the CAW, which represents workers at both GM and Lear, said.
"General Motors will have enough seats to run approximately four, maybe five, hours today and then the Oshawa car assembly plant will cease production," said Chris Buckley, president of CAW Local 222 at Oshawa. "On top of the Oshawa assembly plant, every other auto parts supplier that feeds GM Oshawa will feel this affect as well."
General Motors said it expects production at Oshawa "will be affected early this week" and that it is working to limit the impact.
"GM Canada is hopeful that Lear will reach a resolution with the CAW," said GM spokeswoman Adria MacKenzie, without detailing GM's plans to deal with any disruption.
A spokesman for Lear was not immediately available for comment.
There are about 4,000 assembly line workers at GM's Oshawa plant, and 1,500 auto parts workers in surrounding plants, Buckley said.
Lear's Whitby factory produces and ships car seats to GM Oshawa for assembly in Impala, Buick Regal, Cadillac and Camaro models, Buckley said.
Buckley said the seats cannot be sourced elsewhere, but GM Canada could not immediately confirm that.
A halt in production could affect a host of other GM Canada parts suppliers such as Johnson Controls Inc, Syncreon and Woodbridge Foam Corp, Buckley said.
In another dispute, 65 unionized workers who make exhaust manifolds at Wescast Industries Inc, who are also represented by the CAW, went on strike Saturday morning.
Parts made at Wescast's Strathroy, Ontario, plant are included in GM's Gen IV engines produced at its St. Catharines, Ontario, plant. The engines power Silverado and Sierra models assembled in the United States and Mexico, said CAW national representative Jim Woods.
"We hope that there's not going to be any disruption," of supply, Wescast Chief Executive Ed Frackowiak told Reuters.
"Under the labor laws, we have the right to continue to make parts in that facility by using our salaried staff and that's what we intend to do," he added.