US Secretary of State Condoleezza Rice signed Tuesday what she called a "landmark" missile defence deal with the Czech Republic that drew immediate fire from Russia.
The accord permits the siting of a tracking radar station on Czech soil as part of an extended US missile shield that Washington says is necessary to ward off potential attacks by so-called "rogue" states such as Iran.
"It's truly a landmark agreement," Rice said after signing the accord with Czech Foreign Minister Karel Schwarzenberg. "It is an agreement that is befitting for friends and allies who face a common threat in the 21st century."
During her talks in Prague, Rice charged that Iran's work to build longer-range missiles was proceeding "apace" while at the same time it was defying international calls to halt sensitive nuclear technology.
"Ballistic missile proliferation is not an imaginary threat," the top US diplomat warned.
Rice also reiterated Washington's position that the radar station was not aimed at Russia and instead served as a "building block" not just for Czech and US security but for the "international community as a whole."
The United States wants the radar twinned with interceptor missiles in neighbouring Poland, although negotiations with Warsaw have become bogged down with Polish demands for additional security guarantees.
Rice said she thought it made no sense to visit Poland during her current tour of Europe because the negotiations needed more work.
In a first reaction from Moscow, an unnamed senior foreign ministry official quoted by Interfax news agency warned that the deal did not enhance security but "complicates security issues on a global scale."
Russia is opposed to having the US missile shield on its doorstep.
Analysts say the Russians fear not only a potential long-term threat to their own nuclear deterrent and the security of their airspace but also associate the shield with NATO's enlargement to include Ukraine and Georgia.
NATO endorsed the US missile defence plan at its April summit in Bucharest.
The United States has in the past suggested that Russian inspectors could visit the anti-missile sites, as long as Prague and Warsaw agreed.
"We want the system to be transparent to the Russians," Rice insisted Tuesday.
In Prague, protestors from Greenpeace who fear the missile shield will trigger a new arms race, unrolled a massive image of a target across the city's skyline ahead of Rice's arrival.
Opinion polls regularly show around two-thirds of Czech opposed to hosting the US radar.
But Schwarzenberg expected the deal to be ratified by parliament. "There are sufficient lawmakers who are sufficiently aware of their responsibility and will go forward in strength during the voting," he told reporters.
Czech Prime Minister Mirek Topolanek said the deal reflected a "joint desire to protect the free world".
Prague was the first leg of a three-country tour that will take Rice to Bulgaria and Georgia where she will renew US support for Tblisi's bid for NATO membership -- another bone of contention with Moscow.
She will also try to calm tensions between Moscow and Tblisi over the separatist Georgian regions of Abkhazia and South Ossetia, but she accused Moscow of fueling tensions by failing to consult with Georgia over a presidential order offering Abkhazia direct relations.
"Georgia is an independent state. It has to be treated like one," Rice added.
Georgia regularly accuses Russia of seeking to annex South Ossetia and Abkhazia, and derailing its efforts to join the NATO military alliance. Russia in turn accuses Tbilisi of preparing to take back the breakaway regions by force.
