Presidents Obama and Dmitry Medvedev were ending the seven-year hiatus in U.S.-Russian summitry, with each declaring his determination to further cut nuclear arsenals and repair a badly damaged relationship.
Both sides appear to want to use progress on arms control as a pathway to possible agreement on trickier issues, including Iran and Georgia, the tiny former Soviet republic. Those difficulties and others have soured a promising linkage in the first years after the Cold War and pushed ties between Moscow and Washington to depths unseen in more than two decades.
Mr. Obama, first lady Michelle Obama and their daughters, Malia and Sasha, arrived in Moscow in earl afternoon, local time.
In advance of Mr. Obama's departure, a White House official told reporters the presidents expect to announce progress on negotiations that could lead to a treaty to replace the START I agreement, which expires Dec. 5.
More broadly, the U.S. wants to use the summit to overhaul the U.S.-Russian relationship.
"It's not, in our view, a zero-sum game, that if it's two points for Russia it's negative two for us, but there are ways that we can cooperate to advance our interests and, at the same time, do things with the Russians that are good for them as well," Mr. Obama's top assistant on Russia, Michael McFaul, said in a presummit briefing.
Medvedev said in an Internet address that the two powers "need new, common, mutually beneficial projects in business, science and culture. He added, "I hope that this sincere desire to open a new chapter in Russian-American cooperation will be brought into fruition."
Two things appear certain:
Those deals could be announced at an Obama-Medvedev news conference Monday afternoon after the leaders' scheduled four-hour meeting.
There's been an apparent hardening on both sides over a proposed U.S. missile defense shield in Eastern Europe. Those differences could stall or even preclude an agreement of strategic nuclear warheads. That could kill the hoped-for extension of those talks next year to include cuts in delivery vehicles: long-range missiles, submarines and bombers.
On Friday, Dmitry Peskov, spokesman for Vladimir Putin, the current prime minister and former president, said the Kremlin would not negotiate a replacement to START I unless Mr. Obama clarified plans for the defense system to be based in Poland and the Czech Republic.
The U.S. contends it's designed to protect U.S. allies in Europe from a potential nuclear attack by Iran. The Russians see it as a way of weakening their offensive nuclear strike potential that is are arrayed against the U.S. arsenal. Mr. Obama has been cool to the program, which former President George W. Bush pushed hard.
"The whole issue of missile defense from my perspective is focused on defense of Europe," said Adm. Mike Mullen, chairman of the Joint Chiefs of Staff. "Obviously, the Russians see it differently. So I think we're going to have to work our way through that."
The White House said Sunday that if an agreement comes too late for Senate ratification by Dec. 5, it would look for ways to enforce some aspects on an executive level while waiting for ratification.
Mr. Obama's schedule include an hourlong meeting with Putin on Tuesday. Protocol does not demand he visit the prime minister.
"Prime Minister Putin still has a lot of sway in Russia, and I think that it's important that even as we move forward with President Medvedev, that Putin understands that the old Cold War approaches to U.S.-Russian relations is outdated, that it's time to move forward in a different direction," Mr. Obama said in an interview Thursday with The Associated Press.
Most analysts see Putin as still holding the real reins of power in Russia. Mr. Obama said in the interview, "I think Putin has one foot in the old ways of doing business and one foot in the new."
Putin responded quickly. "We don't know how to stand so awkwardly with our legs apart," he said in televised remarks. "We stand solidly on our own two feet and always look into the future."
Asked if Mr. Obama's comment could be taken as an insult that could make negotiations even more difficult, a White House official said no, that it puts a little pressure on Putin to show he's a "modern guy," reports CBS News chief White House correspondent Chip Reid.
One of the most difficult issues expected in the Putin meeting is his fierce anger at neighboring Georgia. Last August, he sent soldiers, tanks and warplanes to crush the Georgian military after Georgia's leader sought to retake a breakaway region that wants to reunite with Russia.
Putin appears dead set on re-establishing Russia's power and sphere of influence in the former Soviet republics. At the same time, NATO has expanded eastward to include some of those countries. The alliance also is working with Georgia and Ukraine, another former republic, on possible membership in NATO.
In an interesting scheduling twist, Mr. Obama also is to see former Soviet President Mikhail Gorbachev, who negotiated an end of the Cold War with former President Ronald Reagan. There's also to be a second Medvedev meeting after Mr. Obama speaks to new graduates of the New Economic School. It remains unclear if the Russian leaders, who control all television outlets, will allow national broadcast of the speech.
The White House bills the address as the third of four this year on his vision of a new world order. The first was during his visit to the Czech Republic when he laid out a security agenda and concern about nuclear proliferation. After that, he went to Egypt to reach over the heads of leaders of Muslim countries as he sought to improve the U.S. image with the people of the Islamic world.
The last of the foreign policy addresses was planned for Ghana, the final stop on this Obama trip.
Before leaving Washington on Sunday, Mr. Obama spoke by telephone with Turkish President Abdullah Gul, who thanked Mr. Obama for his Cairo speech on U.S.-Muslim relations.
The president does face a major challenge in convincing the Russian people that he genuinely wants to use his office for the betterment of the world even as he seeks to promote a U.S. agenda. He is not well-known to the Russians and most polls show a distrust of the American leader. He certainly enjoys none of the vast popularity lavished on him in Europe and many other places.