Russia declared this fall that it would not renew the Nunn-Lugar Cooperative Threat Reduction Program, which has helped rid the former Soviet Union of thousands of nuclear weapons since the end of the cold war. But in a speech, Mr. Obama chose to interpret the Russian statements as a negotiating position to change the program rather than halt it altogether, The New York Times reports.

"Russia has said that our current agreement hasn't kept pace with the changing relationship between our countries," Mr. Obama said at the National Defense University, where he praised the program's accomplishments. "To which we say, let's update it. Let's work with Russia as an equal partner. Let's continue the work that's so important to the security of both our countries. And I'm optimistic that we can."

Whether Russia is willing to do that remains unclear. Even if it is, Moscow has suggested that it would link the renewal of the program to concessions by the United States on its plans to deploy a missile defense system in Europe intended to defend against Iranian aggression. Mr. Obama was overheard telling his Russian counterpart this year that "after my election I have more flexibility" on missile defense, prompting Republicans to accuse him of plotting to sell out the system.

Mr. Obama made no mention of missile defense on Monday, but in reaching out to Moscow he seemed to be taking the opening step in a postelection dance in which the two countries will re-evaluate their ties. His effort to reset the relationship after a rupture over the Georgia war of 2008 succeeded for a time in stabilizing ties, but the atmosphere has cooled noticeably since Vladimir V. Putin returned to the presidency this year.

In recent months, Russia ordered the United States Agency for International Development to leave and enacted laws focused on nongovernmental organizations receiving foreign financing. As a result, the National Democratic Institute, an American-financed organization that promotes democracy, moved to Lithuania last month, and its counterpart, the International Republican Institute, is likely to follow.

The announcement in October that Russia would not renew the Nunn-Lugar program when it expires in the spring underscored how sour relations had become. Through all the ups and downs over the past 20 years, Nunn-Lugar had always been largely immune to the political tides, in part because Russia saw that having American money and help in slimming down its nuclear arsenal was in its own interest.

Since it began, Nunn-Lugar has helped to deactivate 7,600 nuclear warheads and destroy or eliminate 900 intercontinental ballistic missiles, 500 missile silos, 680 submarine-launched ballistic missiles and 900 nuclear air-to-surface missiles. But the program still envisioned getting rid of hundreds more weapons to meet goals for 2017.

Russia said it would take over the costs and responsibilities of continuing the program, in effect asserting that after its economic and geopolitical resurgence of recent years, it no longer needs foreign help. But Mr. Obama has not given up on preserving the program, although aides said no specific negotiations were under way to renew it.

American officials hope that last month's election will make it possible for the two sides to get back on a better footing. After Mr. Obama's victory, the two presidents spoke by telephone and Mr. Obama accepted Mr. Putin's invitation to visit Russia in 2013. Presumably he would go to St. Petersburg for the Group of 20 summit meeting that Mr. Putin will host in September.

Mr. Obama's outreach to Russia on Nunn-Lugar came during a speech paying tribute to its patrons, former Senator Sam Nunn, Democrat of Georgia, and Senator Richard G. Lugar, Republican of Indiana, who lost a primary this year. Mr. Obama hailed them on Monday as "real visionaries" who "challenged us to think anew, to imagine, after decades of confrontation, how our nations might engage in cooperation."

But, he added: "We're nowhere near done, not by a long shot, and you all know this. There's still much too much material - nuclear, chemical, biological - being stored without enough protection. There are still terrorists and criminal gangs doing everything they can to get their hands on it. And make no mistake, if they get it, they will use it."