U.S. and Russia Appear to Edge Toward Extension of Nuclear Treaty

The United States and Russia on Tuesday appeared to be edging toward a short-term extension of the main arms control treaty limiting the size of the two nations’ nuclear arsenals, after Russia agreed to add a “political obligation” that would freeze its stockpile of nuclear warheads for a year.

It was unclear whether the modest move would be enough for President Trump to extend the New START accord before the presidential election next month, which would allow him to argue that he has gained something in his efforts to nurture a relationship with President Vladimir V. Putin of Russia — and for his determination to avoid criticizing Mr. Putin for human rights violations, authoritarian crackdowns and cyberattacks on the United States.

The treaty expires in February, after the presidential inauguration. Its provisions call for a five-year extension, which Mr. Putin said he was willing to embrace. Joseph R. Biden Jr., the former vice president and Democratic candidate for president, has said the same.

But Mr. Trump has called the treaty deeply flawed and refused a straight renewal, saying at first that China had to become a party to the agreement and then that the Russians had to freeze the weapons in their stockpile but not those deployed.

Russia on Tuesday proposed that both countries make a “political obligation” to freeze their “existing arsenals of nuclear warheads,” but only for one year, an echo of some type of “agreement in principle” that the administration said last week that Mr. Trump and Mr. Putin had reached.

It is something of a concession, as Moscow has previously balked at extending New START negotiations beyond strategic warheads — the focus of the original pact — to include tactical warheads.

Russia has a far larger stock of tactical-range weapons than the United States does, and it has poured money into developing a new generation of nuclear-capable weapons systems, such as new versions of the Iskander tactical missile.

But a “political” commitment to cap tactical and strategic warheads at their current levels for a year would not derail any expansion of Russia’s tactical arsenal in the long term. It would also be difficult to enforce without agreement on elaborate verification procedures.

In a statement, the State Department urged a meeting “immediately” to work out the details; the key stumbling block would be verifying compliance.

The Russian Foreign Ministry closed the door on any additional demands by Washington, saying in a statement that its offer of a one-year extension “can only and exclusively be implemented on the understanding that the United States will not advance any additional conditions with regard to freezing the arsenals.”

This seemed to rule out any discussion of a longstanding demand by the Trump administration that China’s nuclear arsenal be included in any extended version of the New START Treaty, which was signed by President Barack Obama in 2010, or any other amendments. But administration officials appeared resigned to giving that up for the time being.

Russia’s offer on Tuesday keeps alive the possibility that Mr. Trump could get a deal before the election on Nov. 3.

But Moscow expressed annoyance at the Trump administration’s handling of negotiations, complaining that United States officials had not yet formally responded to a proposal by Mr. Putin on Friday for a one-year extension without conditions.

“We have only seen comments made by U.S. officials in the social media,” the Foreign Ministry said.