Barack Obama will be the 44th president of the United States, winning an historic election to become the first African American in the White House.

He told a vast crowd of supporters at a Chicago park that his election showed the world that the United States real strength was not its military but the power of its ideals.

"If there is anyone out there who still doubts that America is a place where all things are possible, who still wonders if the dream of our founders is alive in our time, tonight is your answer," Obama said

Reaching out to Republicans, he called his opponent Sen. John McCain "brave and selfless" and said he looked forward to working with him and his running mate Alaska Gov. Sarah Palin "to renew this nation''s promise."

Speaking to the millions of Americans who voted for the Republican ticket, Obama said: "I hear your voices, I need your help, and I will be your president too."

McCain and President George Bush both called the Illinois senator to congratulate him on his historic victory.

McCain delivered a gracious concession speech soon after polls closed in western states, praising Obama for running a strong campaign and vowing, despite the candidates'' differences, to do everything he could to help the next president face the challenges of his presidency.

"The American people have spoken, and spoken clearly," McCain said, calling for the nation to come together after the bitterly contested poll.

His speech was marred by sporadic booing from the Republican crowd, perhaps showing the difficulties Obama may have in uniting a fiercely divided and partisan country.

Bush congratulated his successor on an "awesome night," and promised a smooth transition to the White House.

The president''s spokeswoman Dana Perino said the president told Obama: "You are about to go on one of the great journeys of life. Congratulations and go enjoy yourself."