A total of 150 deputies out of the 172 present in the 240-seat body voted to ratify the agreement, signed during a visit here in April of US Secretary of State Condoleezza Rice. Twenty voted 20 against it and there were two abstentions.

Foreign Minister Ivaylo Kalfin presented the terms of the agreement to the lawmakers, saying it was "the best way to strengthen the Bulgarian troops' interoperability" and modernize the country's military facilities.

Opponents of the deal said they feared US troops stationed here could embark on a military intervention in a third country or heighten the risk of terrorist attacks on Bulgaria.

Deputies of the small ultra-nationalist party Ataka (Attack) said that "with this agreement Bulgaria is selling its sovereignty" and accused the government of betraying the national interest.

Kalfin contradicted the claim, saying the deal would enhance Bulgaria's security.

"The agreement takes into consideration all national interests of Bulgaria... There are strong enough guarantees that those facilities will be used in partnership. Bulgaria will neither be underestimated nor come second when decisions are taken," he said.

The bases will "strengthen Bulgaria's role in the region and contribute to its security", he added.

The deal, valid for 10 years, concerns the Novo Selo training area near Sliven in the east, the air bases of Bezmer near Yambol in the southeast and Graf Ignatievo near Plovdiv in the south, as well as a storage site near Aitos in the east.

The facilities will be jointly used for training by US and Bulgarian troops. They will host around 2,500 US soldiers at a time, with numbers reaching up to a possible 5,000 during rotation of troops.

The agreement is part of Washington's wider strategy to shift between 60,000 and 70,000 troops from locations in central Europe closer to potential troublespots in the Middle East.

Last December, the US signed a similar deal with Bulgaria's northern neighbour Romania.

The first troops are expected to arrive in Bulgaria in 2007-2008.

Parliament also adopted Friday a special declaration stating that they expect the agreement to operate "in full compliance with Bulgaria's sovereignty and legislation".

It also expressed the lawmakers' conviction that the US would adhere to a 1997 NATO-Russia agreement for non-deployment of nuclear weapons in countries, such as Bulgaria, that have joined NATO in recent years.

The US has "no intention, plan or any other reason to station nuclear weapons on our country's territory", the declaration said.