LONDON (Reuters) -- President Barack Obama and President Dmitry Medvedev will hit the restart button on U.S.-Russian ties by agreeing to begin talks on a new nuclear arms treaty when they meet for the first time on April 1.
But many other contentious issues cloud the outlook, from missile defense to Iran and NATO expansion, before the relationship warms up again.
Their meeting before a G20 summit in London will be an early test for Obama, who is making his debut on the world stage with his first major trip abroad since taking office in January.
His predecessor George W. Bush claimed a personal chemistry with former Russian President Vladimir Putin, although that did not stop several policy disputes and a Kremlin clampdown widely seen as rolling back democratic reforms.
The two new presidents have both signaled a more pragmatic, businesslike approach.
At least one major achievement is expected from the London encounter: agreement to start talks on a new treaty limiting long-range nuclear missiles to replace a pact that expires this year. Expectations are low for much progress on other fronts.
"Nobody should expect a 'Bush heart-to-heart with Putin' kind of experience," said Sarah Mendelson, a Russia expert at the Center for Strategic and International Studies in Washington. "These guys don't operate that way."
Sizing Up Obama
Like other leaders Obama will meet, Medvedev will be sizing him up. Obama also meets President Hu Jintao of China, another world power whose relations with Washington have been rocky.
Medvedev knows what it's like to be under such scrutiny. Since taking office last year, he has yet to put to rest questions whether Putin, who he named as his prime minister, still pulls the strings.
The White House brushed aside criticism from some U.S. conservatives that Obama seems too willing to make concessions to the Russians.
"Nobody believes that a change in our relationship means giving anybody all that they want," Obama spokesman Robert Gibbs said.
Medvedev said in an article in "The Washington Post" that the United States and Russia should rebuild ties because neither can afford "drift and indifference" in their relationship.
Medvedev and Obama are both former lawyers in their 40s. The Russian leader has welcomed Obama's intention to leave behind what Moscow saw as a confrontational U.S. approach over the past few years and has praised a letter from Obama outlining international priorities.
"Frankly speaking, when I was reading it I was surprised by the fact that many views outlined there coincided with my ideas," Medvedev said in a weekend BBC television interview.
Moscow had deplored Bush's drive for NATO membership for the former Soviet republics of Ukraine and Georgia, something Obama signaled would be less of a priority.
Obama has also left the door open to reconsidering the antimissile system Russia bitterly opposes.
However, even while promising to "press the reset button," the Obama administration has made clear it will not recognize what Moscow sees as its "sphere of influence."
Obama also wants Russia to cooperate more in pressuring Iran on its nuclear program, and was expected to push the issue in his talks with Medvedev.
Whatever kind of relationship they forge, it will be nothing like the way Bush and Putin started theirs in 2001, with the U.S. leader saying he had gained "sense of his soul" and trusted his Russian counterpart.