Nikolai Patrushev, the secretary of the powerful security council, said the conditions under which Russia could resort to atomic weapons are being reworked in the main strategy document and will be reviewed by President Dmitry Medvedev by the end of the year.

"The conditions have been revised for the use of nuclear weapons to rebuff an aggression with the use of conventional weapons, not only on a massive-scale but on a regional and even local level," Patrushev told the Izvestia newspaper.

"Variants are under considerations for the use of nuclear weapons depending on the situation and potential of a would-be aggressor," he said.

"In a critical situation for national security, a preventative nuclear strike on an aggressor is not ruled out."

Under its current military doctrine, Russia says it would only carry out a nuclear strike if it were attacked with weapons of mass destruction or if it were the victim of "large-scale aggression" using conventional arms.

Russian and US negotiators are now working furiously to agree on new arms cuts of their nuclear arsenal before a key Cold War-era disarmament treaty expires on December 5.

US Secretary of State Hillary Clinton reiterated the joint drive to achieve new arms reductions by this deadline after talks in Moscow this week.

Since the 1991 Soviet collapse, Russian military planners have relied increasingly on the country's huge nuclear deterrent as the capabilities of its conventional forces have deteriorated.

Patrushev, the former director of Russia's powerful FSB security service, has headed efforts to develop a new military doctrine in recent years to coincide with plans for a radical modernization of Russia's armed forces.

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