US President Barack Obama left behind a week wracked by disaster and war late Friday, launching a five-day tour of Latin America, a region showing fresh potential after its own years of turmoil.

Obama set off for Brazil, Chile and El Salvador fresh from delivering a firm threat of military action to Libya's Muammar Gaddafi and presiding over the US response to Japan's tsunami-quake disaster and nuclear emergency.

Aides were adamant that Obama's trip, designed as a bid to highlight Latin America's growing global economic and diplomatic clout and a trawl for job-creating export markets, would go on despite the multiple world crises.

They say that Mr Obama, with his official Air Force one aircraft and complex entourage can function as President anywhere in the world, and will be as effective on the road as in the White House.

But with multiple press appearances planned during the trip, Mr Obama's message is likely to be somewhat diluted as France, Britain and the Arab world, backed by the United States, move towards action to safeguard civilians in Libya.

Mr Obama will also be closely monitoring latest developments as Japanese engineers backed up by US experts seek to prevent a disastrous meltdown at a quake-damaged nuclear plant in Japan.

Secretary of state Hillary Clinton on Friday made the case for Mr Obama pressing on with his trip, despite the fast-moving foreign policy developments elsewhere in the world.

"As I often say, we have to deal with both the urgent and the important at the same time," Clinton said in a speech at the Center for Strategic and international studies in Washington.

"With President Obama departing for Brasilia. Now is a good time to turn our attention from the urgent events of the day and consider another important part of the world."

Mr Obama plans to highlight an amazing economic leap forward by Brazil, which has lifted millions from poverty and won a new global influence that a new President Dilma Rousseff seems keen to wield.

He will cite Chile's evolution from authoritarian misery to increasingly prosperous democracy as an example for West Asia nations emerging from repression.

And in El Salvador, Obama hopes to show that Washington's engagement can squeeze political oxygen from regional foes like Venezuela's Hugo Chavez.

Analysts and officials said that Obama's five-day journey will be the signature trip within the Western Hemisphere of his first term.

Washington sees the trip as a chance to reassert US weight in a region attracting global interest, and investment dollars, from as far away as China.

"There are, of course, plenty of challenges and they often hog the headlines," Clinton said, noting Latin America's fight against crime, poverty, poor education and inequality.

"But the real story of Latin America on Saturday runs in a very different direction," she said.

"It is a story of political transition and a broad commitment to democratic development, a story of pragmatic leaders who helped turn a once-troubled region into an area of dynamic 21st century economies and societies, a story of active new players on the global stage."

Mr Obama will likely strike a similar theme in Chile for instance, in a speech likely to be compared to his address to the Asia-Pacific region in November 2009, which launched an era of reengagement with a fast rising region.

Part of the President's message may touch on trade, though his message risks being undermined by his failure to secure congressional ratification of trade deals with Colombia and Panama.

Mr Obama will seek a personal connection on Saturday with Brazil's new President Rousseff, who took office at the start of the year, following tense ties with her predecessor Luiz Inacio Lula da Silva.

The leaders will hold a press conference, and Mr Obama will take part in several meetings with business leaders in Brasilia before heading off to savor Rio de Janeiro's tourist spots on Sunday.

In Chile on Monday, Mr Obama will seek to honor a rising nation's embrace of democracy after a difficult transition that aides said may carry lessons for turmoil-wracked nations like Egypt.

Mr Obama will have talks with President Sebastian Pinera and deliver his speech to the region.

On his final stop in El Salvador, Mr Obama will imply that even leftist leaders like President Mauricio Funes can cooperate with the United States, in a signal to US foes like Chavez.