President Barack Obama has begun his first Moscow summit, a series of meetings certain to test his diplomatic skills, but already set to deliver some progress on nuclear reductions and help for the fight in Afghanistan.
The full-scale, two-day US-Russia summit is the first since the early part of the George Bush presidency.
Russia, with its wary public, two-headed leadership and lingering hard feelings, presents a test for Mr Obama.
Much of the world will be watching signs of his relationship with Russia's two leaders, president Dmitry Medvedev and his mentor, Prime Minister Vladimir Putin.
The pattern set now could affect how much co-operation Mr Obama gets in areas in which the US needs help from Russia - chiefly pressuring Iran and North Korea to give up their nuclear weapons ambitions, but also in tackling terrorism, global warming and the economy.
Both sides are talking of improving their ties and wanting to show some early results. Agreements negotiated before Mr Obama showed up give him something to take home, including another step toward the world's two largest nuclear powers reducing their arsenals.
"At the moment I think we are all moderately optimistic, both the Russian side and the American side, so far as I know," Mr Medvedev said.
"I have heard what my colleague President Obama has been saying. And so we are very much looking forward to the visit of the president of the United States."
Mr Obama said that the United States needs to reset its basic relationship with Russia. As he told a Russian-language news channel in the days before the summit: "America respects Russia. We want to build relations where we deal as equals."
The summit starts a week-long trip for Mr Obama that also features G-8 meetings and a visit with the pope in Italy, and a speech in Ghana.
