Poland said Friday it has reached an agreement in principle with the United States on U.S. plans to install a missile defense system on Polish territory.

Polish Foreign Minister Radek Sikorski says that after meetings with U.S. officials, he is satisfied that the United States will deal with security problems that Poland wanted addressed as part of an eventual deal.

The announcement seems to add momentum to a U.S. project that the Bush administration has said it hopes to start building this year. The project has been a major source of tension with Russia and had looked stalled since the Polish government of Donald Tusk sought new demands after taking office in November.

Sikorski did not outline the terms of the deal, but in a joint appearance with Secretary of State Condoleezza Rice after a working lunch, the two officials suggested that the U.S. would help with Polish air defenses, which Poland has asked for in the deal.

"We understand that there is a desire for defense modernization in Poland, and particularly for air defense modernization in Poland," Rice said. "This is something that we support because it will make our ally, Poland, more capable, it will make Poland, as the foreign minister has said, more able to operate with us."

Sikorski said that negotiators would continue to work on the details of an agreement that would allow the U.S. to install 10 interceptors as part of a long range European missile defense system.

"We are not at the end of the road as regards negotiations. We are in the middle of the road," he said. "We have an agreement in principle."

He sought to address likely Russian concern about the U.S. air defense aid by Russia, which has already strongly objected to the missile defense plans. Russia has threatened to retarget nuclear missiles at Poland to counter what it sees as a U.S. attempt to undermine the Russian military deterrent.

"The reinforced Polish air defenses are not directed against anybody," Sikorski said. "They are to enable Poland to be a stronger NATO ally with the United States, to enable Poland to take part in operations, in out-of-area operations, in joint operations."

But the air defense system that Poland has asked for help in building would seem to be aimed at addressing concerns about Russia's threats. Polish officials have previously expressed interest in acquiring short- and mid-range air defenses — Patriot or THAAD missiles — from the United States.

The United States has dismissed Russian concerns about the proposed long range missile defense system saying it is intended to protect Western countries from missiles fired from Iran and would be impotent against Russia's massive arsenal.

"It is true that the United States once had a Strategic Defense Initiative, a program that was intended to deal with the question of the Russian strategic nuclear threat," Rice said, referring to a Reagan era program also known as Star Wars. "This is not that program. This is not the son of that program. This is not the grandson of that program.

If the two sides reach a deal, it would seem to vindicate Tusk and Sikorski's strategy of asking more from Washington in exchange for Poland's support in military operations in Iraq and Afghanistan, as well as the missile defense system.

The previous Polish government of former Prime Minister Jaroslaw Kaczynski, who opened talks early last year, firmly supported the plan without the additional demands.