The US has reconfigured its plans to protect against "rogue" states
Romania has agreed to host missile interceptors as part of a new US defence shield, its president says.
President Traian Basescu said the plan was approved by the defence council. It still needs parliamentary approval.
The US scrapped a previous missile shield, based in Poland and the Czech Republic, which had infuriated Russia.
Instead the new system would provide better defence from "the emerging threat" of Iranian short- and medium-range missiles, a US official said.
Mr Basescu said the system would "protect the whole of Romania's territory", but stressed that it "is not directed against Russia".
He said Romania will host "ground capabilities to intercept missiles" that would be operational by 2015 if approved by parliament.
In the US, state department spokesman PJ Crowley also stressed that the new system was "not a capability that is directed at Russia".
Romania has agreed to host anti-ballistic missile interceptors as part of the administration's "new missile defence plan... to protect US forward-deployed troops and our NATO allies against current and emerging ballistic missile threats from Iran," he said.
Mr Obama's decision to abandon the original plan in September was greeted with enthusiasm in Russia, and came amid attempts to "reset" the relationship between Washington and Moscow.
The anti-ballistic missile shield favoured by former President George W Bush would be replaced by a reconfigured system designed to shoot down short- and medium-range missiles, Mr Obama announced.
He said intelligence suggested Iran was concentrating on shorter-range, not intercontinental, missiles.
The Bush administration plans had infuriated Russia, which threatened to train nuclear warheads on Poland the Czech Republic in response.
The new system is built around ship- and land-based SM-3 missile interceptors.
In October, US Vice-President Joseph Biden visited Poland, Romania and the Czech Republic seeking support for the new system.
Poland has already signed up.