"President Biden pledged to keep the American people safe from nuclear threats by restoring US leadership on arms control and nonproliferation," Blinken said in a statement.

"Today, the United States took the first step toward making good on that pledge when it extended the New START Treaty with the Russian Federation for five years."

Russian President Vladimir Putin signed off last Friday legislation extending the accord.

The New START treaty is the last remaining arms reduction pact between the former Cold War rivals.

Signed in 2010, New START caps to 1,550 the number of nuclear warheads that can be deployed by Moscow and Washington, which control the world's largest nuclear arsenals.

The agreement, which was due to expire on February 5, is seen as a rare opportunity for compromise between Moscow and Washington, whose ties have dramatically deteriorated in recent years.