Poland said Friday it has reached an agreement in principle with the United States on US plans to install a missile defense system on Polish territory. Polish Foreign Minister Radek Sikorski says that after meetings with US 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 US 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 US would help with Polish air defenses, which Poland has asked for in the deal.