Job losses through the expected closure of the Ford Transit van factory are set to be voluntary, according to sources.
Union leaders were locked in a meeting with the company to hear details of the future of the Southampton plant, which employs more than 500 workers.
Union officials said it was a "very worrying time" for the employees at the site, which has been making Transit vans since 1972.
The workforce has been reduced over the years to just 500, operating on a single shift.
The company is also expected to unveil plans for new investment in the Dagenham engine plant in Essex and could sweeten the Southampton closure by offering voluntary redundancies.
An official announcement from Ford on its plans will not be made until later.
Around 2.2 million Transits have been made in Southampton since 1972, although production slumped from 66,000 in 2008 to 28,000 last year after the plant moved to single shift operation.
Ford has unveiled plans to close its factory in Genk, Belgium, with the loss of 4,300 jobs and said more details of its "transformation" plan for Europe will be given.
Stephen Odell, chairman and chief executive of Ford of Europe, said: "The proposed restructuring of our European manufacturing operations is a fundamental part of our plan to strengthen Ford's business in Europe and to return to profitable growth."
Mr Odell is meeting personally with union officials to give them the news.