Bulgarian Prime Minister Boyko Borisov said Friday he favoured taking part in a new US missile defence system in Europe and a US ambassador indicated that talks have already started.

Neighbouring Romania has angered Russia by announcing it wants to host medium-range ballistic missile interceptors as part of a US missile defence system expected to be operational by 2015.

Asked about Bulgaria's stance on the system, Borisov said: "As a NATO member, we take into consideration everything that concerns Europe's security and will undertake the respective measures."

"In my view, we have to show solidarity (with US plans) but Bulgaria's position will depend on parliament and the position of the European Union," Borisov told journalists.

"If you are a NATO member, you have to work for collective security," he said.

The US ambassador to Bulgaria James Warlick hinted in a public lecture that Washington was open for talks with Sofia on the issue.

"There is a role for Bulgaria to play in missile defence, precisely what that is will be in part determined by the interest of the Bulgarian government," he said.

He added that the United States was "at a very early stage of discussion" with Bulgaria and other countries in the region.

"At this stage we would like to consult and to talk through what the possibilities might be and this will happen at the technical level and also at the policy level," Warlick said.

"But given Bulgaria's expressed interest to date, its geography and its cooperation with us in other areas, we hope that the discussions on missile defence will continue and will be productive," he added.

Warlick said the US vision for a missile defence system in Europe was "based on an assessment of the missile threat from Iran and the Middle East."

The new system will "feature deployments of increasingly capable sea- and land-based missile interceptors and a range of sensors in Europe to defend against growing ballistic missile threats," he added.

Warlick played down Russian fears about the system by reiterating President Barack Obama's statement that America wanted "a strong, peaceful, and prosperous Russia."

"Our belief has always been - and it remains - that Russia's legitimate need for security is best served not by having weak, fractious, and impoverished states on its borders -- but rather by having peaceful, prosperous, and democratic neighbours," Warlick said.

"The United States will not ask the Bulgarian government or people to choose between Moscow and Washington," he added.

The United States in September shelved a plan -- that had also angered Russia -- to place missile defence facilities in the Czech Republic and Poland.

The Obama administration has since launched discussions with potential host countries on a revamped missile defence approach.

Romania will start talks shortly with Washington on hosting US missile interceptors as part of the new system, President Traian Basescu said.

Bulgarian press reports cited defence ministry sources as saying that Bulgaria might host either MIM-104 Patriot surface-to-air missiles or SM-3 interceptors for medium and long range ballistic missiles.