US Secretary of State Condoleezza Rice arrived in Prague Tuesday to sign a treaty under which the Czech Republic would host a radar base for a planned US missile defence system.
Rice and her Czech counterpart Karel Schwarzenberg were due to ink the deal on Tuesday afternoon regardless of hurdles it faces in the country's closely-divided parliament, reported dpa.
The centre-right cabinet of Prime Minister Mirek Topolanek is short several coalition votes and will likely have to pull over leftist opposition lawmakers in order to see the deal ratified.
The Czech Republic has rolled ahead with the defence project of importance to the United States, while holding up a key European plan, the Lisbon Treaty designed at reforming the enlarged 27-member European Union.
Washington would also like to place 10 interceptor missiles in Poland as part of the system that it says is being developed against potential long-range missiles from so-called rogue states such as Iran.
The talks in Warsaw have been deadlocked over Polish demands for military aid.
Rice's meeting in Washington Monday with Polish Foreign Minister Radoslaw Sikorski did not break the impasse but Polish and US officials say they remain committed to striking a deal.
Lithuania, a former Soviet state in the Baltics, has already offered to host the base if the negotiations in Warsaw fail.
In Prague, negotiators are yet to conclude talks on a lesser missile shield agreement that defines rules for US troops to be stationed at the planned base in a military zone one hour south-west of Prague.
The Czech cabinet has supported the project despite polls repeatedly showing that more than six out of 10 Czechs oppose the project.
Opponents, who want the government to hold back the talks until after an upcoming US presidential election, plan to protest the deal at Prague's Wenceslas Square later Tuesday.
The plan to build US military bases in former Soviet satellites in central Europe, now members of NATO and European Union, has irked Russia.
Moscow, which has threatened to aim its missiles at the host countries, says it considers the shield a threat to its own nuclear deterrent. Washington has so far failed to ease those concerns.
Rice is also scheduled to visit Bulgaria and Georgia during her trip that ends Thursday.