LONDON (AP) -- Stepping onto the world stage for the first time in his two-month presidency, Barack Obama is holding face-to-face talks with the leaders of the two nations -- Russia and China -- most aggressively challenging the U.S. position atop the global order.
But first up for Obama was a sit-down with British Prime Minister Gordon Brown, the host of the London summit of the world's top 20 economies. The U.S. president and first lady Michelle Obama arrived Wednesday morning at 10 Downing Street, where Brown and his wife, Sarah, greeted them and the four smiled broadly.
Obama is meeting separately Wednesday with Russian President Dmitry Medvedev and Chinese President Hu Jintao. Officials in both countries have called for a new global currency to end the dollar's dominance.
Dramatic in itself, the suggestion is also a sign of broader questions about whether U.S. status in the world could be threatened by the rise of a competing power bloc.
It's not likely that the new currency idea will gain immediate traction. But Steven Schrage, an international business expert at the Washington-based Center for Strategic and International Studies, said it could eventually if the Obama administration doesn't tackle the perception that the wave of massive stimulus spending in the United States could create unsustainable debt levels.
"People will be very closely reading the tea leaves," Schrage said.
That's one reason the public will see little of the meetings. Both are being held at the U.S. ambassador's residence, with the news media only allowed into the room before the talks take place and without the ability to ask questions.
The Obamas had a low-key arrival in Britain Tuesday night to launch an eight-day, five-country European tour.
The central focus is the summit on the global economic meltdown. Obama's preparations continued even as he flew across the Atlantic. He consulted by phone with the summit host, British Prime Minister Gordon Brown.
The meetings open with a working dinner Wednesday night and continue throughout Thursday.
Obama and Brown will cap their own meetings with a joint appearance before the press.
With Brown's political future in doubt, Obama is later squeezing in talks with Brown's main rival -- David Cameron, the leader of Britain's opposition Conservative Party.
In the afternoon, Obama heads to Buckingham Palace for an audience with Queen Elizabeth II.
With U.S.-Russia relations having deteriorated in recent years to lowest point since the early 1980s, the Obama administration has announced its desire to "press the reset button." The Kremlin has made clear it believes it is up to Washington to open the effort with concessions.
Obama has indicated less enthusiasm than predecessor George W. Bush for a proposed new U.S. missile defense system based in Eastern Europe, an idea that has enraged Russia. Another key area of discussion is the possible replacement of the dying 1991 Strategic Arms Reduction Treaty, which limited the world's two largest nuclear arsenals. START expires Dec. 5. Obama and Medvedev are expected to announce talks on a new pact.
They would be the first major arms control negotiations since 1997. But a thicket of disputes makes meeting the deadline unlikely.
With Moscow eager to boost its battered prestige, Reginald Dale, a CSIS Europe scholar, said Obama can't afford to employ the soft touch with Russia.
"Medvedev will be taking the measure of Obama," Dale said. "It's not enough just to say, 'Let's be friends.' ... They think, oh, here's someone I can lead up the garden path."
Obama's talks with Hu are sure to address Beijing's concerns about the safety of its position as Washington's biggest foreign creditor, with about $1 trillion in U.S. government debt. For the U.S., there are fears that any Chinese flight away from those investments would erode the U.S. ability to spend more on recession-fighting.
For China, unusually forthright of late in challenging the U.S.-led global order, its goal is a greater say in how international finance is regulated and managed.
Beijing and Washington also have sparred over military matters.