PRAGUE, Czech Republic – The United States and the Czech Republic signed an initial agreement Tuesday allowing the U.S. military to build a radar station southwest of Prague as part of an antiballistic missile defense system in Eastern Europe.

The United States and its allies say the system will protect against attack by Iran and other enemies, but the plan has drawn intense criticism from opponents in the Czech Republic and from Russia, which calls the missile shield unnecessary, destabilizing and a threat to its security.

U.S. officials hope to start constructing the $3.5 billion defense system next year and complete it by around 2012.

Recent opinion polls show that about two-thirds of Czech citizens oppose hosting the missile-tracking stations. Many members of the Czech Parliament, where the government controls just half of the 200 seats, oppose the plan, including the Green Party, which is a junior member of the coalition government.

Moreover, Poland, which the U.S. government hopes will host a base with 10 interceptor missiles, has so far refused to agree, reportedly demanding multimillion-dollar security guarantees – including upgrades in its air defenses – from the United States.