WINDSOR, Ont. -- Autoworkers from across Ontario vowed Friday to keep fighting General Motors' plans to shutter a prominent plant in the province as the company announced an improvement to its financial forecast for the year ahead.

Members of Unifor, the union representing the bulk of the 2,600 workers affected by the company's plans to close its plant in Oshawa, Ont., gathered in Windsor, Ont., to voice their ongoing opposition to the move.

The union had bussed members in from Ontario communities several hours away, including Kitchener and Brampton. They gathered at GM's Windsor headquarters to hold a rally during an investor's meeting that was taking place in nearby Detroit, where the company announced its rosier financial prospects.

"We're not a happy group here in Canada, and we're damn well prepared to show you how mad we really are," Unifor President Jerry Dias said at the rally.

Dias said members would continue with a string of actions to try and get the company's "absolute attention," including appearing at a major auto show in Detroit next week.

"GM is going to live up to the commitment that they made to us in 2016 that they will be no closures during the life of our agreement," he said.

Days before Friday's rally, unionized workers at the Oshawa assembly plant staged two work stoppages to protest their employer's decision to close the facility.

But GM, which previously announced that the Oshawa plant would be one of five North American operations to close in the coming years, has unequivocally stated that the decision is final and was made as the company shifts its focus towards electric and autonomous vehicles.

The company did offer more positive news on Friday, however, strengthening its pretax profit estimate for 2018 and predicting even stronger performance for the year ahead.

The company forecasted 2018 pretax per-share profits would exceed expectations laid out in the third quarter, saying it would likely surpass the target of between US$5.80 to US$6.20 it set at the time. For 2019, the company boosted its profit guidance up to between US$6.50 and US$7 per share.

The relatively sunny profit forecast came despite declining sales for the company in the U.S. and slowing sales in China. GM also plans to exit several car lines in the U.S. in the coming year.

CEO Mary Barra told investors the company did not foresee any additional job losses beyond the 14,000 positions that will be cut as the five plants wind down.

"We've made all the announcements that we need to make," she said. "We're continuing to transform the company."

Dias sat down with GM earlier this week to talk about proposals the union had made to extend the life of the Ontario plant, but came away empty-handed.

The union has emphasized the wider economic impacts of the shut-down and released a study Wednesday putting some hard numbers to its claims that the move would deal a devastating blow to the provincial economy.

The estimates the closure of the plant by the end of the year will result in 14,000 fewer jobs in Ontario and 10,000 fewer jobs outside the province by 2025, compared with keeping the assembly plant open. Those would include 4,400 jobs at GM Oshawa and its parts suppliers in Ontario that would be lost in 2020, Unifor said.

The closure would also cut Ontario's GDP by $5 billion and mean $330 million less provincial government revenue next year, the study estimated.

GM has said the options suggested by the union to keep the Oshawa plant open, such as extending the life of the Chevy Impala and Cadillac XTS produced at the factory or shifting production slated for Mexico to the plant, are not economically viable.

-- By Michelle McQuigge in Toronto, with files from the Associated Press.