KIEV, Dec 6 (Reuters) - Ukraine's Economy Ministry   proposed the government extend grain export quotas set to expire on December 31 to March 31 next year, according to a draft resolution published on Monday. The draft resolution proposed issuing additional quotas for exports of 500,000 tonnes of wheat exports and 1.0 million of maize. The initial grain export quotas allow exports of 500,000 tonnes of wheat and 2.0 million of maize until the year-end.