BUCHAREST (Reuters) - The United States has asked to boost the number of troops and aircraft it has stationed at an airbase in NATO ally Romania, President Traian Basescu said on Tuesday, as tensions between the West and Russia simmer over neighbouring Ukraine.

U.S. forces have used the Mihail Kogalniceanu air base on the Black Sea in eastern Romania since 1999. It is a major hub for U.S. troops leaving Afghanistan and is located not far from Ukraine's Crimea peninsula, annexed last month by Russia.

"The U.S. embassy in Bucharest has asked for support from Romanian authorities to expand current operations at the Mihail Kogalniceanu base," Basescu said in a letter of notification to the speaker of Romania's lower house of parliament.

The U.S. request would add up to 600 U.S. troops to the roughly 1,000 currently stationed in Romania and would also increase the number of military aircraft there, the letter said.

Foreign ministers from the 28-nation NATO alliance were meeting in Brussels on Tuesday to discuss ways to boost the security of member states in ex-communist eastern Europe after Russia's occupation and annexation of Crimea.

(Reporting by Luiza Ilie; Editing by Gareth Jones)