"We have reached a deal with the United States on the shield," after Washington agreed to meet Poland's key demand for defense aid separate from the anti-missile system, Tusk told Polish news channel TVN in a live interview.

"We would start with a battery under US command, but made available to the Polish army. Then there would be a second phase, involving equipping the Polish army with missiles," Tusk added, emphasizing that negotiators had reached a "preliminary deal."

The agreement has been reached after more than 18 months of back-and-forth, often terse, negotiations between the two countries. Its conclusion carries an especially symbolic weight in the aftermath of Russia's incursion into Georgia in recent days.

In return for agreeing to host 10 US missile interceptors on its soil, Poland will receive Patriot air defense missiles and increased military cooperation with the US, according to a report by Poland's PAP news agency

US and Polish negotiators were meeting in Warsaw on Thursday in the latest in a series of talks that formally began in May 2007.

Czech deal already complete

In July, the Bush administration signed a deal with the neighboring Czech Republic on hosting a radar base -- the other part of the system to be based in the two ex-communist countries. Poland and Czech Republic joined NATO in 1999 and the European Union in 2004.

Before the latest talks in Warsaw, top Polish government officials said a new US proposal was on the table and that Russia's military assault on Georgia had given an impetus to the missile defense talks.

A key Polish concern is boosting its air defenses after Moscow threatened to target the planned bases in its former direct sphere of influence.

Russia strongly opposes the US plan, despite assurances from Washington that the shield would target ballistic missile threats from countries like Iran and was not meant to undermine Russia's nuclear deterrent.

The Interfax news agency cites Konstantin Kosachev, who chairs the foreign affairs committee in the Russian lower house of parliament, as saying the agreement will spark "a real rise in tensions in Russian-American relations."