The Opel plant in Antwerp will be closed, according to sources.
The plant's future has been under review since GM decided not to sell Vauxhall/Opel, but its 2300 staff had been hoping for a stay of execution.
GM is seeking to reduce its European capacity by around one-fifth, cutting 8000 jobs in total.
"They did not back down from the decision to close Antwerp. Now [Opel CEO Nick] Reilly has announced that this would be implemented," a company source told Automotive News Europe.
However, a GM Europe spokesman said on Tuesday that no final decision on the Antwerp factory has been made.