Americans have elected Democrat Barack Obama as their first black president, in a transformational election which will reshape US politics and reposition the United States on the world stage.

President-elect Obama, 47, will be inaugurated the 44th US president on January 20, 2009, and inherit an economy mired in the worst financial crisis since the 1930s, two wars in Afghanistan and Iraq and a nuclear showdown with Iran.

Television networks projected his victory over Republican John McCain after President-elect Obama solidified traditional Democratic states and cut deep into the Republican territory which his rival needed to control to win the White House.

Senator McCain conceded defeat in front of a large crowd of supporters and media in Phoenix, Arizona.

"The American people have spoken and they have spoken clearly," he said.

"A little while ago I had the honour of calling President-elect Barack Obama to congratulate him on being elected the next president of the country that we both love."

President George W Bush also telephoned President-elect Obama to congratulate him on his "awesome night," according to White House spokeswoman Dana Perino.

"Mr President-elect, congratulations to you. What an awesome night for you, your family and your supporters. Laura and I called to congratulate you and your good bride," she quoted Mr Bush as telling President-elect Obama.

Seventy-two-year-old Arizona Senator McCain urged Americans to rally behind the President-elect, saying he planned to help Obama tackle the many challenges facing Americans.

"Whatever our differences, we are fellow Americans and please believe me when I say no association has meant more to me than that," he said.

"It is natural tonight to feel some disappointment but tomorrow we must move beyond it."

Senator McCain commended President-elect Obama on his achievement and said he respected his ability and perserverance.

"It's a historical election and I recognise the special significance it holds for African-Americans," he said.

"I wish the outcome had been different, my friends.

"She is one of the best campaigners I've ever seen," he said of Republican vice-presidential candidate Sarah Palin.

Senator McCain called for unity and said running for the presidency was the greatest honour of his life.

The news came sooner than many in the crowd gathered in Chicago's Grant Park had expected: immediately after polls were closed on the west coast.

Tears, hugs, and chants of "Yes we can!" and "Obama! Obama!" rang into the air as his supporters greeted the news.

"Today I am proud to be a black American," cheered Rosemary Morris as she sat with two friends at the foot of a statue on the park's edge as early results were coming in.

"This is a wonderful, wonderful, wonderful day."

Meteoric rise

President-elect Obama's historic inauguration will complete a stunning ascent to the pinnacle of US and global politics from national obscurity just four years ago and close an eight-year era of turbulence under President George W Bush.

He will take office with Democrats holding a monopoly in power in Washington, after an epochal election which sparked a rare generational and political realignment and finally snuffed out an era of Republican control.

President-elect Obama is promising to renew bruised ties with US allies, and to engage some of the most fierce US foes like Iran and North Korea. He has vowed to tackle climate change and provide health care to all Americans.

His presidency also marks a stunning cultural shift with President-elect Obama, the son of Kenyan father and white mother from Kansas, the first African-American president of a nation still riven by racial divides.

Heralding change

When he launched his campaign on a chilly day in Illinois in February 2007, President-elect Obama forged a mantra of change which powered him throughout the longest, most costly US presidential campaign in history.

With a stunning grassroots political movement, powered by massive multi-million dollar fundraising, President-elect Obama first beat Hillary Clinton, and the Democratic Party's then-preeminent political machine.

He strode towards victory by capturing the states of Pennsylvania, the key battleground which Senator McCain needed to win to keep his long-shot hopes of victory alive.

In a sweet moment for Democrats, he also seized the states of Ohio and Florida, making a clean sweep of battleground states. and captured New Mexico and Iowa, two states won by President Bush in 2004 to close out Senator McCain's possible route towards the White House.

The state of Colorado also fell for the Democratic candidate, for only the second time since 1964.

President-elect Obama had led national and battleground polls and had capitalised on the fear of Americans pitched into the deep financial crisis, especially as he appeared to be presidential in a string of debates.

Senator McCain had argued that President-elect Obama was too inexperienced to be US commander in chief and would pursue "socialist" redistribution policies that would leave the economy mired in recession.

Senator McCain, 72, an Arizona senator, would have been the oldest man ever inaugurated for a first term in the White House.

- AFP