The countries last week announced plans to extend the agreement, even as the Biden administration has stepped up criticism of Russia over the jailing of opposition leader Alexei Navalny, its involvement in a massive hack of U.S. agencies and other issues.
“Especially during times of tension, verifiable limits on Russia’s intercontinental-range nuclear weapons are vitally important. Extending the New START Treaty makes the United States, U.S. allies and partners, and the world safer," Blinken said. “An unconstrained nuclear competition would endanger us all.”
U.N. Secretary-General Antonio Guterres welcomed the extension, U.N. spokesman Stephane Dujarric said. “It’s a first step of reinvigorating ... the nuclear arms control regime.”
The outgoing Trump administration made a late bid to extend the treaty, but Russia rejected its conditions.
The treaty was due to expire Friday. Both houses of the Russian parliament voted unanimously last month for the extension, and President Vladimir Putin signed the bill.
That was after President Joe Biden and Putin talked and agreed on the extension, part of a quick round of diplomacy by the less than month-old U.S. administration to keep the treaty going. The extension doesn't require formal congressional approval in the United States.
The Biden administration will also work on control measures for China's smaller but growing arsenal of nuclear warheads, Blinken said.
Edie Lederer in New York contributed.