LONDON AND MOSCOW — President Obama and Russian President Dmitry Medvedev agreed Wednesday to open negotiations on a treaty that could slash their nuclear arsenals by a third, part of what they described as a step "to move beyond Cold War mentalities" in relations between Washington and Moscow.
The agreement to undertake significant arms control talks emerged from the first face-to-face meeting between the two leaders, and included a promise by Obama to visit the Russian capital this summer to pursue the talks.
"Over the last several years, the relationship between our two countries has been allowed to drift," Obama said. "What I believe we've begun today is a very constructive dialogue that will allow us to work on issues of mutual interest."
The overture toward Russia was in keeping with the accommodating tone Obama projected on the eve of a summit on the global economic crisis.
In London on Wednesday, the president downplayed differences with European leaders over clashing prescriptions for healing the world economy. And he reached out to China and Russia, powers with which the United States has had frequently prickly relations, saying he would visit both countries this year.
But it was the Russian question that Obama dealt with in depth. The renewed friction between the onetime Cold War foes developed over issues such as NATO expansion to countries once part of the Soviet Union, and soured further last summer when Russian troops fought a war with Georgia, a U.S. ally.
The consensus on the need for new nuclear arms talks was the most concrete expression yet of the Obama administration's decision to opt for improved ties with Moscow rather than greater confrontation.
In turn, Medvedev said he was prepared to cooperate on nonproliferation, among other issues.
"It is important to note that there are many points on which we can work," he said. "And indeed there are far more points where we can come closer, where we can work, rather than those points on which we have differences."
For Russia, the push for a new nuclear treaty has as much to do with diplomatic clout as with strategic necessity, said Nikolai Zlobin, director of the Russia program at the Center for Defense Information in Washington.
"This is an area where Russia and the United States together can force the rest of the world to accept their view," he said. "It makes Russia a global power again. Russia feels like it's back to old times."
Although hailed by arms control experts, word of the agreement was not seen as a surprising development. Obama is on record saying he favors beginning talks, and Russian officials have been eager to come up with a new pact to replace the Strategic Arms Reduction Treaty, which expires in December.
The world's two largest nuclear powers are limited to arsenals of 1,700 to 2,200 nuclear warheads, under a subsequent treaty signed in Moscow in 2002.
But administration officials say they are seeking a treaty with stricter verification measures -- an accord, arms control experts say, that could also reduce the ceiling on warheads to 1,500 or lower.
"This has been on the radar for quite some time," said Daryl Kimball, executive director of the Arms Control Assn. in Washington. "The fact that they've put it front and center of their bilateral agenda is important."
Obama and Medvedev met with reporters after their talk, laughing at each other's jokes -- Obama said he preferred not to visit Russia in the winter -- and smiling broadly as they shook hands.
But while the two leaders struck a friendly tone in the meeting, officials acknowledged a series of obstacles to an agreement that could be ready when START expires.
Russia remains intent on persuading Obama to scuttle the former Bush administration's plans for missile defense facilities close to Russia's border, in Poland and the Czech Republic.
The two sides did not discuss the matter Wednesday, though the Obama administration has expressed a coolness toward deploying the system. The joint statement issued in London acknowledged Russia's concerns.
Moscow in recent weeks also has taken a hard-line stance on lingering strategic disputes with the United States.
Medvedev has repeated warnings against expanding the North Atlantic Treaty Organization alliance close to the Russian border, and has emphasized the need to update his country's aging nuclear arsenal.
White House aides said the two leaders acknowledged significant points of disagreement during their meeting. Obama told Medvedev that his administration will not recognize the independence of the breakaway regions of South Ossetia and Abkhazia in the former Soviet republic of Georgia, where Russian forces responded to a Georgian attack on rebels last summer by mounting an invasion.