US Defense Secretary Robert Gates accused Moscow today of "mauling and menacing small democracies" but said today's Russia did not pose a threat to the world like the Soviet Union.
Mr Gates also said Russia's recent military action in Georgia was a Pyrrhic victory - costing Moscow far more in the long term than any short-term gains it achieved.
"The Russian leadership might seek to exorcise past humiliations and aspire to recapture past glory along with past territory," he said. "But mauling and menacing small democracies does not a great power make."
Moscow was internationally condemned for sending troops and tanks into Georgia to stop Tbilisi's attempt to reassert control over the pro-Russian, separatist region of South Ossetia.
Russia later recognised South Ossetia and another rebel Georgian region, Abkhazia, as independent states, and on Wednesday signed treaties to protect them from Georgian attack.
Earlier today Russian president Dmitry Medvedev said he did not want disputes with the West to push Russia behind a new Iron Curtain, and blamed Nato for provoking the conflict in Georgia.
"We are in effect being pushed down a path that is founded not on fully-fledged, civilised partnership with other countries, but on autonomous development, behind thick walls, behind an Iron Curtain," Mr Medvedev said in an address to a gathering of civil society groups.
"That is not our path. For us there is no sense going back to the past. We have made our choice," he said.
He also said the Nato alliance's role in the Georgia conflict showed it was unable to provide security in Europe, creating a need for a new security mechanism.
"That is understood even by those who in private conversations with me say ... 'Nato will take care of everything'. What did Nato secure, what did Nato ensure? Nato only provoked the conflict, and not more than that."
Mr Gates' remarks came a day after a speech by Secretary of State Condoleezza Rice that was highly critical of Moscow.
While Mr Gates, a former CIA director who built his career on knowledge of Russia and the Soviet Union, echoed some of Rice's words, he also sought to put the conflict over Georgia in perspective.
"In reality, Russia's policies are born of a grievance-based desire to dominate its 'near abroad', not an ideology-based effort to dominate the globe," he said in a speech at Blenheim Palace, birthplace of Winston Churchill, near Oxford.
"And Russia's current actions -- however egregious -- do not represent the existential and global threat that the Soviet Union represented," he told a conference organised by consulting firm Oxford Analytica.
"Russia's conventional military remains a shadow of its Soviet predecessor in size and capability," he said.
"Images of the Russian armour and artillery overwhelming Georgia's tiny military -- an active force of some 30,000 troops - does not reverse that reality," Mr Gates said.
"I believe the Georgia incursion will, over time, be recognized as a Pyrrhic victory at best and a costly strategic overreach," he declared.
He said Europe and Washington would help Georgia rebuild and take decisions in the months ahead that could affect Russian bids for membership of the World Trade Organisation and the Organisation for Economic Cooperation and Development.
"Russia's recent behaviour raises questions about how successful we can be in trying to pursue a constructive relationship," he said.