US troops are also allowed to use three training ranges in southeast and central Romania.
Calin Popescu Tariceanu, Romania's prime minister, lauded the agreement, saying that for decades after 1945 many Romanians had "only one hope: that the American troops would come and free us from communism."
Today, however, he said, "Romania is no longer a victim looking for a savior, but a partner of the United States in the fight against terrorism."
Politicians from the country's nationalist opposition parties have opposed the plan however.
"It is very serious for Romania to become a buffer state between two major nuclear powers," Lucian Bolcas, a senior leader of the nationalist Great Romania Party, said, referring to the US and Russia.
Russia has criticized the deployment of US troops in former communist countries such as Romania and opposed the planned construction of a US anti-ballistic missile system in Poland and the Czech Republic.
An initial series of US-Romanian exercises - with about 200 US troops and more than 250 Romanian troops participating - began on April 20 at Kogalniceanu and is due to end Friday.