The United States signed an agreement on Friday to establish three military bases in Bulgaria as it shifts troops from old Cold War positions to smaller installations closer to the Middle East and Africa.
Under the deal, the US will deploy 2,500 soldiers on short rotations to Bulgaria as it draws down tens of thousands of troops from bases in Europe and Asia.
"The agreement indeed will enhance our co-operation, allowing the shared use of Bulgarian training facilities and strengthening our ability to operate militarily," said US Secretary of State Condoleezza Rice after a signing ceremony on the sidelines of a meeting of Nato foreign ministers in Sofia.
Bulgaria, an ex-communist country of 7.7 million, has been eager to repay Washington for supporting its 2004 Nato entry, backing the United States in Iraq despite widespread public opposition to the war.
The 10-year agreement includes the Bezmer airfield and Novo Selo shooting range, both near Bulgaria's border with Turkey, and the Graf Ignatievo airfield in central Bulgaria.
The US said the first troops would most likely arrive next year. Under the arrangement, Washington may launch attacks against third countries from the bases after consulting Bulgarian authorities. Both sides have said the facilities will be shared and used mainly for training.