Russia has vowed to take military action against the US if America goes ahead with plans to build missile defence installations on its old Cold War turf in eastern Europe.
The threat from Moscow came just hours after US Secretary of State Condoleezza Rice signed a deal with the Czech Republic to construct a radar tracking station on its soil.
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“If a US strategic anti-missile shield is deployed near our borders, we will be forced to react not in a diplomatic fashion but with military resources,” a Russian foreign office statement said.
“There is no doubt that the grouping of elements of the strategic US arsenal faced towards Russian territory” could lead Moscow to “take adequate measures to face the threats to its national security,” it added.
The US's plans for a tracking station in the Czech Republic is part of an extended shield that Washington says is necessary to ward off potential attacks by so-called “rogue” states such as Iran.
Washington also wants a radar system twinned with interceptor missiles in neighbouring Poland, although negotiations with Warsaw have becomed bogged down with Polish demands for additional security guarantees.
Former Soviet state Lithuania has offered itself as an alternative site should the Polish talks stall.
Russian President Dmitry Medvedev on Monday clashed with US President George W. Bush over missile defence at their first face-to-face meeting during the G8 summit in Japan.
“There are topics on which we are making progress, such as Iran and North Korea, there are topics on which we diverge, such as the missile shield and European matters, but there are possibilities for agreement,” Mr Medvedev said.
Analysts say Moscow fears not only a potential long-term threat to its own nuclear deterrent and the security of its airspace but that it is also wary given NATO's prospective enlargement to include the former Soviet states of Ukraine and Georgia.
NATO endorsed the US missile defence plan at its April summit in Bucharest.
Shared radar base plan
The US has suggested Russian inspectors could visit the anti-missile sites, as long as Prague and Warsaw agreed.
While still president in February, Russia's Prime Minister Vladimir Putin said Moscow would point its missiles towards Ukraine, Poland and the Czech Republic if NATO enlargement or the proposed US missile shield got
In July 2007, Moscow announced its intention to deploy missiles in the Kaliningrad enclave between Poland and Lithuania, if Washington did not accept a Russian remplacement to the anti-missile project.
Russia had at the time suggested the solution of sharing a radar base in Azerbaijan with the US. It reiterated this proposal for a joint Russia-NATO anti-missile shield on Tuesday.
“Our proposals to create a collective anti-missile defence system on the principle of equal security for all remain on the table,” said a “highly-placed official from the Russian Ministry for Foreign Affairs,” as cited by Interfax news agency.