NATO nations made public Friday a long-standing offer to Russia aimed at getting Moscow to renew its commitment to a key Soviet-era arms pact, just days ahead of a key summit.

Russia announced at midnight on December 11 that it was suspending participation in the Conventional Forces in Europe (CFE) treaty, which limits the deployment of troops and military equipment.

"This situation cannot be sustained indefinitely," a NATO statement said.

"Russia's 'suspension' risks eroding the integrity of the CFE regime and undermines the cooperative approach to security which has been a core of the NATO-Russia relationship and European security for nearly two decades."

NATO said the United States, with allied backing, had proposed some six months ago "a package of parallel actions, which, taken together, address all of the concerns Russia has raised with regard to CFE and related issues".

Under the offer, NATO allies would agree to move forward on ratifying the CFE treaty as Moscow resolved "outstanding issues" related to its forces in Georgia and Moldova.

Signed in 1990 and modified in 1999, the CFE places precise limits on the stationing of troops and heavy weapons from the Atlantic coast to Russia's Ural mountains -- a mammoth agreement that helped resolve the Cold War standoff.

Russia attributes its freeze to the failure of NATO members to ratify a revised 1999 version of the treaty but Moscow has also been riled by US plans to deploy an anti-missile shield in two former Soviet satellite states.

NATO countries have said they will only ratify the CFE treaty once Moscow lives up to a pledge made in 1999 to pull its troops out of former Soviet republics Georgia and Moldova.

Despite the offer, both sides have been unable to end the deadlock.

"The Russians tell us that because they have ratified the adapted version of the treaty, it's up to us to take the first step," a NATO diplomat said, on condition of anonymity.

"But we tell them that they have to respond to the offer we made them before last year," he said.

He added that, for the moment, "no one had crossed any red line but that, on both sides, this situation cannot last indefinitely."

NATO leaders are to meet with Russian President Vladimir Putin in Bucharest on April 4, where the treaty, as well as differences over Kosovo and the US missile defence shield are likely to be hot issues.

When asked about NATO's move Friday, Russian ambassador at the alliance, Dmitry Rogozin, told AFP that the "publication of the offer is aimed at putting pressure on Russia."