Poland and the United States appear closer to a deal that would allow US missile defense interceptors to be installed on Polish territory. Polish Foreign Minister Radek Sikorski said the two sides had agreed in principle after he had received assurances on Friday that the United States would help Poland strengthen its short- to medium-range air defenses. The two sides did not elaborate on the terms of their breakthrough, and it remained unclear whether the United States had made specific promises to provide air defense systems. Friday's announcement seems likely to further aggravate tensions with Russia, which has opposed adamantly the US missile defense plans for Europe, which would also include a radar array in the Czech Republic. The announcement seems to restore 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 Poland's new government, headed by Prime Minister Donald Tusk, sought new arrangements after taking office in November. In a news conference by Sikorski and US Secretary of State Condoleezza Rice on Friday, the two officials suggested that the United States would help with Polish air defenses, which Poland requested 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 United States 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." Any eventual deal also would have to be approved by the Polish parliament, and the US Congress would have to approve the financing. On Friday, Sikorski sought to address likely Russian opposition by Russia to the US air defense aid. Russia has already threatened to retarget nuclear missiles at Poland to counter what it sees as a US 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 for which Poland has asked for help in building would seem to be aimed at addressing misgivings about Russia's threats. Polish officials previously have expressed interest in acquiring short- and mid-range air defenses from the United States to include Patriot or THAAD missiles. Friday's development is likely to figure in talks between Tusk and Russian President Vladimir Putin when the two meet in Moscow on Feb. 8. The United States has dismissed Russian objections to 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 intended to deal with the question of the Russian strategic nuclear threat," Rice said. The program, also known as Star Wars, was supported by 1980s President Ronald Reagan. "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 should 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 conservative Polish government, headed by former Prime Minister Jaroslaw Kaczynski, opened talks early last year and firmly supported the plan without the additional demands.