Former Soviet foreign minister Eduard Shevardnadze said on Monday that Russia's decision to suspend its participation in a pact limiting conventional forces in Europe was the first step towards a new "Cold War".
Russian President Vladimir Putin suspended Russia's observance of the Conventional Forces in Europe (CFE) treaty last Saturday.
"I believe this step is the first move towards reviving the Cold War," Shevardnadze, a liberal-minded foreign minister under Soviet leader Mikhail Gorbachev who helped to negotiate the pact, told Reuters.
Russia had previously criticised NATO members for not ratifying the updated version of the treaty, and says it is concerned by the concentration of NATO forces along its borders. Putin cited "national security" for Russia's action.
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But Russia is also upset about Washington's plans to site parts of an anti-missile shield in Poland and the Czech Republic, saying these are a threat to Russian security.
Shevardnadze, widely seen as one of those who brought about an end to the Cold War, said: "This step by Moscow is a response to Washington's decision to deploy elements of its anti-missile shield in Europe."
Shevardnadze, who was president of Georgia until 2003, also said he was concerned that Russia might deploy additional armed units along its border with Georgia as "an element of extra pressure".
Georgia's relations with its former imperial master Russia are badly strained. While Georgia pushes for full NATO membership and closer ties with the West, Russia exerts pressure on it through energy and transport links and by backing the pro-Moscow rebel regions of Abkhazia and South Ossetia.
NATO members have declined to ratify the new CFE until Russia withdraws its troops from ex-Soviet Georgia and Moldova, but Russia rejects any link between the issues.
The CFE was signed in 1990 as a way to avoid conflict in Europe between NATO and the communist Warsaw Pact by limiting the amount of heavy weaponry deployed and stored between the Atlantic and Russia's Ural mountains.
It was amended in 1999 to take account of the collapse of the communist bloc.