Moscow has officially agreed to extend the only remaining nuclear arms treaty with the United States for another five years, with Russian President Vladimir Putin signing the move into law on Friday. The decision was previously approved by Russian lawmakers.

The New START treaty limits the number of deployed nuclear warheads for both the US and Russia. Both sides can only have up to 1,550 ready for use on intercontinental missiles and heavy bomber bases. The treaty also imposes various other restrictions on the two countries' respective arsenals. According to US data cited by the Bulletin of Atomic Scientists last year, the US had 1,373 deployed warheads to Russia's 1,326. The deal was set to expire next week.

Putin spoke with US President Joe Biden on Tuesday, with the two leaders agreeing to keep the New START in place. The US does not require congressional approval to extend the deal.

Beijing says no

With the Trump administration withdrawing from the Intermediate-Range Nuclear Forces Treaty (INF) in 2019, the deal is the only major accord regulating the nuclear rivalry between Moscow and Washington.

Following the INF collapse, Putin warned that the US showed no interest in keeping the New START treaty alive.

"We said a hundred times that we are ready [to extend it]," but Washington is "not conducting any talks" on the matter, Putin said at the time.

The US eventually started talks last year but suggested a change of the terms and adding China to the Obama-era accord. Beijing rejected the initiative. Russia also insisted on prolonging the deal without changes, and the talks stalled.

No more 'Open Skies' for US and Russia

Last November, the Trump administration said it was pulling the US out of the Open Skies Treaty. The accord, which involves 34 states, is a trust-building measure that allows countries to fly unarmed aircraft over military facilities of other signatories for surveillance purposes. Earlier this month, Moscow said it too would abandon the deal.

But with Biden taking the reins in the White House last week, the climate seems to be shifting. Both sides have recently signaled they are willing to work on arms control, including non-nuclear threats.

dj/sms (Reuters, AP, AFP, dpa, Interfax)