Poland and the United States reached an agreement Thursday that will see a battery of American missiles established inside Poland - a plan that has infuriated Russia and threatened to exacerbate tensions with the region's communist-era master. Polish Prime Minister Donald Tusk - speaking in an interview televised on news channel TVN24 - said the United States had agreed to help augment Poland's defenses with Patriot missiles in exchange for placing 10 missile defense interceptors in the Eastern European country. "We have crossed the Rubicon," he said, referring to the US consent in meeting Poland's demands. Tusk said the deal, signed late Thursday in Warsaw, includes a "mutual commitment" between the two nations to come to each other's assistance "in case of trouble." The deal still needs approval from Poland's government and parliament and from US Secretary of State Condoleezza Rice. The clause on mutual assistance appeared to be a reference to potential challenges from Moscow, which says the missile shield represents a threat to Russia. Washington insists, however, it is not meant for Russia but instead is aimed at protecting Europe from attacks by countries in the Middle East. Moscow had threatened to redirect missiles toward Poland if the country agreed to host elements of the US missile defense shield. On Thursday, Russian lawmaker Konstantin Kosachev warned that the deal would also spark "a real rise in tensions in Russian-American relations," according to the Interfax news agency. The recent Russian military incursion into Georgia, along with its bombing of Georgian military outposts and airfields, has rattled former Soviet satellites in Eastern Europe. Poland said the conflict in Georgia underlined Poland's need for US military assistance if it were to cooperate on the US missile defense shield. "I am satisfied," Foreign Minister Radek Sikorski, said after US negotiator John Rood and his Polish partner Andrzej Kremer initialed the agreement at the Foreign Ministry. "Only evil people should be afraid of our agreement," he said. The United States has also reached an agreement with the Czech government to place a radar component of the shield in that country. That deal still needs approval from Czech parliament. The Polish premier said Thursday's agreement for the countries to come to one another's defense was "a step toward real security for Poland," as it would take too long for NATO to respond if Poland were threatened. It would take "days, weeks to start that machinery," Tusk said. "It is not a good situation when rescue comes to dead people. We must ensure our security from the very first hours of a possible ... conflict," he said. Tusk said the US met the Polish demands for a permanent presence of Patriot missiles, which "will be able to effectively protect our territory." The deal was reached after more than 18 months of back-and-forth, often terse, negotiations between the two countries.