The agreement to station a U.S. radar in the Czech Republic was signed on July 8 by U.S. Secretary of State Condoleezza Rice and Czech Foreign Minister Karel Schwarzenberg.
Lubomir Zaoralek, the opposition party's deputy chairman and parliament's vice speaker, said: "The two agreements on the placement of an anti-missile radar signed by [Prime Minister] Mirek Topolanek's government must be examined in the country's Constitutional Court."
The lower house of parliament began debates last Wednesday on the missile defense treaty and a Status of Forces Agreement on the deployment of U.S. troops at the radar base, to be built in the Brdy military district, about 90 km (55 miles) south of Prague.
According to polls, 70% of Czech citizens oppose the deployment of the anti-missile radar.
The government's signing of the agreements does not guarantee that the radar will be built. The documents must be ratified by both houses of parliament, then signed by President Vaclav Klaus.
The radar is part of a planned missile shield system that would also include the deployment of 10 interceptor missiles in Poland. The U.S. says it needs the Central European shield to protect against attacks by "rogue states" such as Iran.
The plans are fiercely opposed by Russia, which sees the missile shield as a threat to its national security and the international system of nuclear deterrence.
Russian President Dmitry Medvedev has vowed to "respond appropriately" to the deployment of the missile shield.