Romania's president says the United States has asked to increase the number of troops and aircraft it has stationed at a Black Sea air base in eastern Romania.

The U.S. wants to add up to 600 troops to the 1,000 currently stationed at the base of Mihail Kogalniceanu and military aircraft "for specific missions," President Traian Basescu said Tuesday.

The base, which can accommodate up to 2,000 troops, is a major hub for U.S. forces and equipment leaving Afghanistan and is a few hundred kilometers (miles) from Crimea, which Russia annexed last month.

It was used by the U.S. in 2001 as an air transport hub early in the Afghanistan war and about 7,000 American troops used it as a staging base for deployment into northern Iraq in 2003.