FILE PHOTO: Unifor President, Jerry Dias, helps launch the Unifor #SaveOshawaGM campaign by unveiling its Tree of Hope in Memorial Park in Oshawa, Ontario, Canada, December 13, 2018. REUTERS/Carlos Osorio

TORONTO (Reuters) - The head of Canada's auto union said on Monday he was set to meet with General Motors Co GM.N executives in Detroit on Tuesday to discuss the automaker's Oshawa, Ontario, assembly plant, scheduled to shut down in December 2019.

Unifor, the union that represents workers at the plant, has vowed to block its closure.

“I have no idea if it’s going to be positive or negative,” Jerry Dias, national president, said in an interview. “I’m optimistic it will be positive, but I’m not even going to try to guess what they’re going to tell us tomorrow.”

After meeting with GM executives in Detroit on Dec. 20, Dias told reporters the automaker would respond to the union’s proposals by Monday.

Dias said he did not think Chief Executive Mary Barra would be at the Tuesday meeting.

He said one option would be to extend operations for nine months, when regular contract talks are scheduled to begin: “That gives us all time to figure out a long-term solution,” he said.

The Oshawa shutdown is part of a broad restructuring announced in November. GM also plans to close four U.S. plants, eliminating a total of about 15,000 jobs in North America.

Barra promised in early December to keep an “open mind” about another affected plant, Ohio’s Lordstown Assembly.

GM has said the Oshawa closure affects 2,973 assembly line jobs. The company employs 8,150 in Canada.