WARSAW, Poland — Talks over plans to locate an American missile defense base on Polish soil may take some time after the new government in Poland stepped up its demands, Assistant Secretary of State Daniel Fried said.

“The Polish government has made clear it has some hard questions, it wants to see Polish security increased,” Mr. Fried told a press conference in Warsaw yesterday, without giving details. “The stakes are high.”

America wants to deploy 10 missile interceptors in Poland and a radar system in the Czech Republic as part of its missile defense shield, a forward line of defense against possible attacks by so-called rogue states such as Iran. Prime Minister Tusk of Poland said on taking office in November that he would take a harder stance over the plans than his predecessor to ensure Poland received additional safeguards. Foreign Minister Radoslaw Sikorski said in an interview with daily Gazeta Wyborcza published on January 5 that it wasn’t possible yet to say whether an agreement can be reached by the end of 2008.

While ties between Poland and America have traditionally been strong, relations have become more strained since the new government requested closer military cooperation in return for an accord over missile defense. At the same time, it announced a withdrawal of Polish troops from Iraq by the end of this October. Poland has commanded a multinational force in the American-led mission since August 2003.

A Defense Department spokesman, Geoff Morrell, said on January 15 that some statements by the Polish government were “unhelpful,” adding that without America’s help, Poland may not have been able to join the North Alliance Treaty Organization in 1999. Mr. Sikorski said yesterday that estimates of American military aid to Poland in Iraq were too high.