Mr. Obama spoke at a news conference next to his British counterpart, Prime Minister Gordon Brown, and both called for, and predicted cooperation among the leaders of the world's richest nations at Thursday's G20 Summit in London.
The president acknowledged differences in opinion he and Brown have with some other G20 nations, which are skeptical of the U.S.-British policy of pumping money into the economy to defeat negative growth trends, but, he said: "We can only meet this challenge together."
"I came to listen, not to lecture," Mr. Obama assured fellow leaders. "Having said that," he added, "we must not miss an opportunity to lead."
He prodded nations to spur growth and work together on regulatory reform, but not to fall into the kind of protectionism and other mistakes that helped fuel the Great Depression.
"That is a mistake that we cannot afford to repeat," Mr. Obama warned.
"The EU has taken serious steps," the president said, praising moves already made by European and other G20 countries. "They have all initialed serious stimulus packages."
"Our goal is simply to make sure that each country, taking into account differences in economic circumstances, is doing what is necessary to promote economic growth. The United States will do its share."
Both Brown and Mr. Obama expressed confidence that the G20 would come together and agree on meaningful moves to revive global stock markets, banks and boost consumer confidence.
Brown even proclaimed that the world was "hours" away from agreeing on a cohesive global economic plan.
President Obama arrived at 10 Downing Street in London Wednesday morning for private talks with Brown, prior to the joint news conference.
Launching his first full day of meetings in Europe, Mr. Obama and first lady Michelle Obama were greeted by Brown and his wife, Sarah at the entrance to the prime minister's official residence.
|Photos: Obama In London|
The president has his first full day in London. (Photo: AP)
The four of them waved and smiled for photographers before heading inside.
There were very few protesters anywhere near Downing Street, but thousands were gathering at other points in the British capital to demonstrate against global warming, capitalism, war and everything else under the sun.
And sun there was. The Obamas arrived to the nicest week of weather London has had this year to date. The president and Brown took note, pointing up at the sky and smiling during their handshake on No. 10's door step. Mr. Obama also opened his remarks at the news conference with a comment on the sunshine.
Mr. Obama and Brown are in synch on how to revive the flagging global economy - Brown was the first world leader to embrace the concept of investing billions of dollars of taxpayer money back into his domestic economy, in the form of economic stimulus packages.
Both men have urged the rest of the world's economies to follow suit, but some of their counterparts in Europe . The leaders of Germany, China and France, most notably, see the looming threat of inflation as too daunting to keep spending state funds on economy-boosting packages, which have yet to prove effective.
A day-by-day guide to one of the most closely watched presidential trips in recent memory.
Mr. Obama called this week's G20 summit in London "a critical meeting at an obviously critical time in the world's economy."
But, as CBS Evening News anchor Katie Couric , this is also a critical opportunity for him.
Together, they will lobby the other G20 leaders to give their plans time to work, and to keep the money flowing.
Mr. Obama was scheduled to meet later Wednesday with Queen Elizabeth II at Buckingham Palace, British opposition leader David Cameron, and Russian President Dmitry Medvedev.
Mr. Obama is on a five-country European tour. The centerpiece of the president's London stay is Thursday's summit at London's ExCel Center.