Russia said Wednesday that it would agree to slash its nuclear arsenal to match proposed US cuts as long as the reductions took the form of a binding legal treaty.

The agreement must take the form of “a binding legal document that forsees radical, real, and verifiable reductions of strategic offensive weapons, up to the ceiling of 1,700 to 2,200 nuclear warheads 10 years from now,” the foreign ministry said in a statement.

US President George W. Bush has proposed to cut the US nuclear arsenal from around 6,000 warheads to between 1,700 and 2,200, while Russian President Vladimir Putin had previously said he was prepared to slash the Russian nuclear arsenal to 1,500 warheads.

The disarmament issue has shaken their warming strategic relationship, with Putin calling “a mistake” Bush’s unilateral decision to withdraw from the 1972 Anti-Ballistic Missile treaty to pursue the development of US missile defense.

The US on Wednesday declined to comment on Moscow’s demand for cuts within the context of a binding legal treaty saying only that it had held “productive” and “substantive” arms control talks this week with Russia.

“We found it productive, we found it a substantive discussion, but at this point I don’t think I can go into more specifics on that,” State Department spokesman Richard Boucher said.

“The form of the agreement would be subject to discussion. We know the Russian position, they’ve stated it publicly before and our position is that we’ll talk about it. That’s what we’re doing,” he added.

On Tuesday, Russia criticized the United States for destabilizing the international arms control regime.

The fact that Russia has requested a binding legal treaty may further sour disarmament talks, as the United States has said it wants a more informal agreement.

The Russian foreign ministry announcement came one day after Under Secretary of State for Arms Control and International Security John Bolton held disarmament talks in Washington with Russian Deputy Foreign Minister Georgy Mamedov.

A second round of negogiations is due to be held in Moscow on February 19.

The ministry said it would like to sign the agreement when Bush visits Moscow later this year.

US President George W. Bush announced on December 13 that Washington will withdraw from the ABM accord to pursue a missile defence project free from the constraints imposed by the treaty.

Since then Moscow has avoided a confrontation with Washington in favour of talks aimed at redefining their strategic relations.