Putin, speaking to top generals less than two weeks before December 2 parliamentary elections, said the NATO military alliance had built up its forces close to Russia’s borders.

“We see that military resources of certain states and members of the NATO alliance are being built up right by our borders and in contravention of previously reached agreements,” Putin said in remarks shown on state television. “We cannot allow ourselves to remain indifferent to the obvious ‘muscle-flexing’,” Putin said.

He said strategic nuclear forces — which control Russia’s long-range nuclear missiles — should be ready “to deliver a swift and adequate response to any aggressor”.

Putin, who has hiked military spending substantially over the past eight years, has sought to boost Russia’s international clout after the chaos following the fall of the Soviet Union.

Talking tough about Russia’s military is immensely popular locally. Polls show it strikes a chord with millions of Russians who crave for the Soviet Union’s once mighty military and superpower status.

NATO is viewed with suspicion in Russia, where Kremlin officials say expansion eastwards into the Baltic states and Central Europe shows the alliance is being used by the United States to threaten Russian interests.

Kremlin talks tough

Putin says he is friends with US President George W Bush. But he has berated the United States for seeking to impose its will on the world and sowing havoc with unilateralist policies, such as the war in Iraq.

Moscow and Washington have clashed over US plans for a missile defence shield in Europe, differing views of Russian democracy, the future of the Serb province of Kosovo and the war in Iraq, though on Iran there has been some cooperation.

Putin said Russia’s suspension of the Conventional Forces in Europe Treaty, a key arms treaty limiting forces in Europe, was one way to counter NATO's “muscle-flexing”.