"This would mean we are back in the sphere of influence where the Russians have the final say," Kaczynski, who is staunchly pro-American and deeply suspicious of Russia, told a news conference in Warsaw.
Poland and the United States have been engaged in protracted talks over a U.S. request to place 10 interceptor missiles in northern Poland as part of a U.S. missile shield for Europe and North America against possible attacks from "rogue states," including Iran.
Poland continues to insist on the modernization of its armed forces, primarily its air force and air defense, with financing to be provided by Washington, in exchange for agreeing to the placement of the U.S. base on its territory.
Warsaw is particularly interested in U.S. short- and medium-range missile systems, such as Patriot PAC-3, THAAD and ground-based AMRAAM.
Prime Minister Donald Tusk earlier told reporters: "We approach this issue from the assumption that the missile defense base, on its own, does not strengthen Poland's security. A decision on this must be accompanied by a number of other decisions that will objectively, and materially, improve Poland's security."
The U.S. already gives Poland $27 million per year in military funding, the highest to any European ally, and the Bush administration earlier this year offered an extra $20 million per year. However, Poles say the funding level is still not enough.
U.S. Secretary of State Condoleezza Rice is expected to arrive in Warsaw on July 10. Experts believe that the formal talks on the U.S. missile base in Poland may be finalized just before or during her visit.