Part maker for General Motors (GM), Inteva Products, saw workers walk off the job Tuesday morning in protest of the upcoming closure of the Oshawa plant, which Inteva supplies.

Unifor national president Jerry Dias said in the afternoon that the fight to keep Oshawa open is also for those non-union workers in the feeder plants.

He didn't say if the union coordinated the job walk-off, but said Inteva workers were walking off in solidarity with those in Oshawa.

Just over 2,500 people working at the Oshawa assembly plant will lose their job once the plant closes this year.

"We will have more announcements tomorrow," said Dias. "And I promise you and I assure you this, this will be the worst auto show that General Motors will ever face in their history of the auto shows here in Detroit."

He did not give any more details on the campaign the union is bringing to catch GM's attention, only saying there will be "a series of events" planned.

Dias gave reassurances of provincial and federal governments being on board with him to fight for GM to reverse its decision as well.

Katerina Georgieva/CBC More

If GM doesn't reverse its decision to close, it might seem like a signal of the end of the company's expansion in Ontario, but premier Doug Ford said that isn't the case.

He had a one-hour meeting in Detroit, Mich. with "two presidents from General Motors" Tuesday.

Ford said the company's presence in southwestern Ontario will be growing "in other sectors," like high-tech manufacturing in Markham.

"Also in Oshawa, the CAMI plant, they're not going anywhere and neither is St. Catharines," Ford told CBC News immediately following the meeting.

Ford also had a meeting with Michigan's new governor, Gretchen Whitmer, at the auto show.

In a statement released Tuesday afternoon, Ontario says Ford heard from auto company executives how the province can support auto manufacturing jobs in Ontario.

"We continue to listen to workers and employers about how best to support the creation of good new jobs and help people find those jobs," said Ford in the statement.