Washington, Nov. 5 - Democrat Barack Obama, fresh from a historic election win as the U.S.’s first black president, turned Wednesday to the sobering challenge of steering a new course for a country grappling with two wars abroad and the threat of a prolonged recession at home.

Obama easily defeated Republican John McCain in a triumph that reflected Americans’ weariness with eight years of Bush administration rule.

His first task will be to begin building - over the next 2 1/2 months - a Democratic administration that will help him make good on the promises of change that carried him to the White House. Obama will name Illinois Congressman Rahm Emanuel as his chief of staff Wednesday, aides told the Associated Press on condition of anonymity ahead of the announcement.

Public address

Obama’s speech before 240,000 supporters on election night clearly acknowledged the difficulties - domestic and international - he will face.

"We know the challenges that tomorrow will bring are the greatest of our lifetime - two wars, a planet in peril, the worst financial crisis in a century," Obama said. "There is new energy to harness and new jobs to be created, new schools to build and threats to meet and, for us to lead, alliances to repair."

In electing Obama, the son of black man from Kenya and a white woman from Kansas, American voters broke with the country’s sad history of racial divisions.

It was an accomplishment recognised both by supporters and by McCain who, in conceding defeat, acknowledged the "special pride" black Americans must be feeling Tuesday night.

"Change has come to America," Obama told cheering supporters in Chicago.

Obama tore up the U.S. political map in triumphing over McCain, a veteran Republican senator who was saddled with President George W. Bush’s legacy. Towards the end of his presidency, Bush was almost as unpopular at home as he is abroad.

"Change has come to America," Obama told cheering supporters in Chicago.

Obama’s choice as vice president, Sen. Joseph Biden, predicted during the campaign that as president, Obama would be tested by a foreign power. Russia on Wednesday signaled that it may be first to do so.

President Dmitry Medvedev, in a speech Wednesday, said Russia would deploy short-range missiles close to its borders with NATO countries Poland and Lithuania, in response to U.S. plans for a missile defence system in Europe.

Medvedev did not congratulate Obama, but blamed the U.S. for the global financial crisis and for allegedly provoking Russia’s war with Georgia in August.

When Obama takes office Jan. 20 as the 44th U.S. president, he may face more difficult challenges both at home and abroad than any new U.S. president since the Great Depression.

But he will do so with many allies in Congress, as the Democrats expanded their majorities in both the U.S. House and Senate. And he will take office with broad popular support.

Statistics

He scored a decisive victory Tuesday. With most U.S. precincts tallied, the popular vote was 52.3 percent for Obama and 46.4 percent for McCain. That made him the first Democrat to receive more than 50 percent of the popular vote since Jimmy Carter in 1976.

In the state-by-state contest that under the U.S. constitution determines the presidency, Obama needed only 270 votes to claim the win. But he sailed to victory with 349 to McCain’s 147, with three states still too close to call.

Voter turnout, still being counted, was expected to shatter records.

Supporters welcomed Obama’s victory with delirious celebrations in cities across the U.S., as supporters cheered, danced and cried.

In Washington, hundreds took to the streets near the White House, carrying balloons, banging drums and chanting "Bush is gone!"

Prominent black leaders were overjoyed, weeping unabashedly in public.

The Rev. Jesse Jackson, who had made two White House bids himself, said on ABC television’s "Good Morning America" on Wednesday the tears he shed after Obama’s victory were about those who had struggled so long for racial equality.

From Hong Kong, retired Gen. Colin Powell, a black Republican, called the senator’s victory "a very very historic occasion," and predicted that Obama would be "a president for all America."

New generation

Obama’s victory marked the rise of a new generation of American leadership, after 16 years of presidents who came of age during the Vietnam War era. Obama. 47, was still a child when most U.S. troops came home.

It was also Americans’ final, symbolic rejection of Bush’s presidency.

Bush’s popularity soared after the Sept. 11, 2001, terrorist attacks, then collapsed with his administration’s bungled response to Hurricane Katrina in 2005, the war in Iraq, and to the regulatory lapses that many think led to the U.S. financial crisis.

The race was the longest, most expensive and most riveting in memory. Both Obama and McCain had been on the campaign train for almost two years.

McCain concedes

McCain called his former rival to concede defeat - and mark the end of his own 10-year quest for the White House. "The American people have spoken, and spoken clearly," McCain told disappointed supporters in Arizona.

But, after a fiercely negative campaign, he pledged to support Obama and "do all in my power to help him lead us through the many challenges we face."

Bush congratulates

Bush added his congratulations from the White House and promised a smooth transition. "What an awesome night for you," he told Obama shortly after the race was decided.

An Obama presidency offers the prospect of a new style and tone in American foreign policy.

Obama has said he will try to withdraw U.S. troops from Iraq in 16 months and has called for a new opening to U.S. adversaries, such as Iran and Cuba. He has urged the closing of the Guantanamo Bay prison and favors cap-and-trade systems to reduce global warming.

Popularity

Internationally, Obama is hugely popular - a sharp contrast to Bush. Part of his appeal is his personal story that highlights American multiculturalism: Besides his Kenyan father, he has a half-sister who is the daughter of an Indonesian.

In his campaign, Obama mined a deep vein of national discontent, promising Americans hope and change throughout a nearly flawless 21-month campaign for the White House.

He first soared into the national spotlight with his electrifying speech at the 2004 Democratic National Convention, when he made his first run for the Senate. He offered a message of unity to a country mired in partisan anger.

In a grueling primary battle, he managed to raise more money and out-maneuver the front-runner, former first lady Hillary Rodham Clinton.

Hillary to support

After Obama’s victory Tuesday, Clinton called and pledged her support. Americans, she said in a statement, "voted for change, and refused to be invisible any longer."

Throughout his campaign, Obama was the target of false rumours about his religion, his ethnicity and his patriotism. Some pointed to his middle name of Hussein to claim that Obama, a Christian, was Muslim - something a significant number of Americans would find unacceptable.

In his race against McCain, Obama was steady and focused on the economy - voters’ biggest concern - and linking McCain to Bush.

McCain, 72, was a tough rival for Obama. He is widely admired for his enduring 5{ years as a prisoner of war during the Vietnam War. His reputation as a maverick gave Republicans hopes of winning over independents and moderate Democrats.

But McCain had an uphill fight. He tried without success to portray Obama as too radical and inexperienced, casting him as an advocate of high taxes and socialism.

McCain also tried to shake up the race by naming Alaska’s young conservative governor, Sarah Palin, as his vice presidential running mate. The choice energized much of the Republican base, but her lack of experience and poor performance in interviews worried many voters.