GENK, Belgium, Oct 24 (Reuters) - Ford Motor Co is poised to tell unions on Wednesday that it will close its factory in the Belgian town of Genk, which employs 4,300 workers, as it tries to stem losses in Europe and match capacity to tumbling demand.

Ford has summoned staff representatives to a meeting with European executives at 0700 GMT without giving an agenda, according to unions. Ford Europe managers, including chief executive Stephen Odell, are then scheduled to meet the Flemish regional government in Brussels.

The plant in eastern Belgium makes the Mondeo mid-size car and Galaxy and S-MAX minivans, but all three models are nearing the end of their current life cycles.

According to sources with knowledge of production plans, Ford is prepared to wind down the factory and build the next generation Mondeo elsewhere.

The plant has operated on a four-day week for much of 2012, according to unions, with only 15 more production days planned this year and none in December. Workers began blocking the gates when reports of the possible closure emerged on Monday.

Ford, which will present third-quarter results on Oct. 30, doubled its European loss forecast for 2012 to $1 billion in July and said action was needed to "decrease our production to match real demand".

Unions had said last month they were more optimistic about Genk's future after Ford set a date to start production of the new Mondeo there in October next year.

However, the sources who asked not to be identified said the tentative start date was not a reprieve for Genk.

If confirmed, Genk would be the second Belgian car factory to close in two years, after General Motors' Antwerp site. The scale of Ford's European losses has increased speculation that it will join PSA Peugeot Citroen and GM's Opel in announcing a major plant closure.

Peugeot announced plans in July to cut 8,000 more jobs and close a plant in Aulnay, near Paris. Opel is in talks with unions on a restructuring plan leading to the eventual closure of its factory in Bochum, Germany.