Union leaders have been called to a meeting with motor giant Ford amid fears that the firm's UK van factory in Southampton is to close.
Union officials said it was a "very worrying time" for the 500 employees at the Southampton 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.
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 today.
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 will meet personally with union officials to give them the news.
Ford employs around 11,400 workers in the UK at plants including Dagenham in Essex, Halewood on Merseyside and Bridgend in South Wales.
Unite assistant general secretary Tony Burke said: "This is a very worrying time for the UK workforce. Unite is currently working hard alongside its European colleagues to get clarity about Ford's plans but the union will not be adding to the current speculation."