Russian Defence Minister Sergei Ivanov has said his country does not rule out a pre-emptive military strike anywhere in the world if the national interest demands it.
Putin: Russia's nuclear arsenal as deadly as ever.
He said that Russia faced foreign interference in its internal affairs and instability in neighbouring states as well as classic threats such as the proliferation of weapons of mass destruction, international terrorism and the drugs trade
President Vladimir Putin, who met Mr Ivanov on Thursday, added that the Russian military still possessed a formidable nuclear arsenal.
A report by the Defence Ministry also called on Nato to review its strategy, warning that otherwise it would be necessary to pursue "a radical reconstruction of Russian military planning, including changes in Russian nuclear strategy".
Mr Putin has signed an agreement with US President George W Bush to cut the two countries' nuclear arsenals by two-thirds in 10 years.
But many in Russia's military establishment are angry about former East Bloc allies joining Nato, as the Western alliance moves into traditional spheres of Russian influence.
Mr Ivanov was speaking in Moscow at a conference of the Russian military leadership.
In an apparent reference to the US-led invasion of Iraq, Mr Ivanov said that the use of force without UN approval could encourage countries to acquire a nuclear potential.
But he said that Russia could not rule out the use of force itself "if the interests of Russia or its alliance obligations demand it".
Russia's new national security doctrine, unveiled last year, allows the use of all possible force, including nuclear weapons, to oppose attacks, if all other methods fail.
Previously, Russia said it would only use nuclear weapons if its national sovereignty was under threat.
Addressing Thursday's meeting, Mr Putin said Russia had "at her disposal a considerable... stockpile of heavy ground-launched strategic missiles...".
"Their combat characteristics, including the surmounting of any systems of anti-missile defences, are unrivalled," he said.
The president added that the arsenal included many strategic nuclear missiles never before deployed.