(Adds quotes from Lavrov, background)

OSLO, April 26 (Reuters) - NATO expressed grave concern at Russian President Vladimir Putin's decision to freeze Moscow's commitments under a European arms control pact on Thursday.

NATO Secretary General Jaap de Hoop Scheffer said Russian Foreign Minister Sergei Lavrov confirmed Putin's announcement suspending Russia's implementation of the Conventional Forces in Europe (CFE) pact to NATO ministers at a meeting in Oslo.

"That message was met by concern, grave concern, disappointment and regret," de Hoop Scheffer told a news conference. "The allies are of the opinion that the CFE is one of the cornerstones of European security," he added.

Minutes later, Lavrov defended the Russian move at a separate news conference.

"I think that we cannot be unconcerned by the fact that NATO military infrastructure is creeping up to our borders," he said.

Lavrov said Russia had been complying with the treaty and it was time for NATO to show it was serious about it, warning: "Unless our partners do that we will withdraw from the treaty."

The CFE Treaty was negotiated in the months after the Cold War among the then-22 member states of NATO and the Warsaw Pact countries with the goal of achieving verifiable reductions in conventional military equipment. Only Belarus, Kazakhstan, Russia and Ukraine have so far ratified an adapted 1999 version.

NATO has for long insisted that Russia withdraw its remaining troops from Georgia and Moldova before its members ratify a revised version of the CFE.

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