MOSCOW — The Kremlin on Friday welcomed the Biden administration’s offer to extend a nuclear disarmament treaty that is set to expire next month, signaling, as had been expected, that Russia intends to cooperate with the United States on nuclear security despite President Biden’s pledges to otherwise pursue a harder line with Moscow than his predecessor.
The agreement was last updated in 2010 and puts a cap on the number of strategic nuclear warheads both sides can deploy. It does not limit the number of strategic weapons kept in storage or smaller nuclear explosives intended for tactical use on a battlefield.
The Trump administration had resisted approving a five-year extension under a provision in the original treaty, while seeking to expand the agreement to also cover China’s arsenal. That approach unraveled when Beijing declined to negotiate.
Mr. Biden has long favored approving a simple extension of the existing treaty, as has the Kremlin.
“We can only welcome the political commitment to extend this document,” Dmitri S. Peskov, the Kremlin spokesman, told journalists on a conference call on Friday.
The treaty caps the number of strategic nuclear weapons the sides can deploy at 1,500 warheads each. It is symbolically important as the last of the late Cold War-era disarmament deals still in force, despite the souring relations between Russia and the United States.
Other treaties have fallen by the wayside. The United States withdrew from a treaty banning nationwide missile defense systems under the Bush administration, citing new threats from Iran and North Korea.
In response, Russia pulled out of a treaty governing conventional troop deployments in Europe. The Trump administration, citing what it said was cheating by Russia, withdrew from a treaty banning intermediate-range missiles, weapons with short flight times that had put the Cold War adversaries on hair triggers for nuclear war.
Mr. Biden asked for the full five-year extension, the most time available under the treaty’s terms, in hopes of preventing a nuclear arms race at the same time that the United States was expecting continuing low-level competition with Russia around the world, according to his aides.
“This extension makes even more sense when the relationship with Russia is adversarial as it is at this time,” Jen Psaki, the White House press secretary, said on Thursday.
The Biden administration and the Kremlin have just two weeks to negotiate the extension before the treaty expires on Feb. 6. Complicating the talks, Mr. Biden has said that he intends to retaliate against Russia for a sweeping hacking operation last year that breached government and corporate computers in the United States.
Mr. Biden is also expected to take a more forceful position on Russia’s military interventions in Libya, Syria and Ukraine, and on the poisoning and arrest of the country’s most prominent domestic opposition figure, Aleksei A. Navalny.
Mr. Peskov, the Kremlin spokesman, said that Russian officials would study the Biden administration’s offer before formally agreeing to an extension. He noted that Ms. Psaki had said that the treaty could be extended without new conditions.
“Before now, this wasn’t the conversation,” Mr. Peskov said. “Certain conditions for the extension were put forward, some of which absolutely didn’t suit us. So, let’s first get acquainted with what the Americans are offering,” before responding.