BARCELONA, Dec 13 (Reuters) - Chinese carmaker Great Wall Motor has withdrawn its interest in taking over Nissan's main plant in Barcelona, which is scheduled to shut by year-end, the Spanish government and Nissan unions said on Monday.

Great Wall did not respond to a request for comment.

Coming just weeks before Nissan's three Barcelona plants are scheduled to close, the decision is a blow to authorities and leaves the fate of around 1,600 direct jobs up in the air, as GWM was the main contender to take over the largest factory.

The Industry Ministry said in a statement the Chinese company had said it would not proceed with the project. Last week, national and regional authorities sent an improved proposal when GWM reportedly cast doubts on its initial interest in the plant.

Another meeting on the plant's future will be held on Dec. 17 to discuss striking a deal by the end of the year with other possible investors, the statement said. (Reporting by Joan Faus; Additional reporting by Brenda W. Goh and Isla Binnie; editing by Nathan Allen and Jason Neely)