WASHINGTON, Aug 28: Senator Barack Obama made history on Wednesday night, becoming the first black American to win presidential nomination of a major US party.

“The journey will be difficult. The road will be long,” conceded Mr Obama while urging his supporters to continue to back him all the way to the White House on Nov 4.

Mr Obama made a surprise appearance before a roaring crowd at the Democratic Party convention in Denver, Colorado, to introduce his vice-presidential candidate Senator Joe Biden.

He received a strong endorsement from his one-time rival, Hillary Clinton, who came close to winning the Democratic nomination earlier this summer.

“With eyes firmly fixed on the future, and in the spirit of unity with the goal of victory,” Ms Clinton said, “with faith in our party and our country, let’s declare together with one voice right here, right now that Barack Obama is our candidate and he will be our president.”

Several hours later her husband, former president Bill Clinton, also vigorously supported Mr Obama’s candidacy. “Barack Obama is ready to lead America and restore American leadership in the world,” he said. “Barack Obama is ready to be president of the United States.”

Other senior leaders of the Democratic Party were equally enthusiastic in backing Mr Obama.

“Barack Obama will end this politics of distortion and division,” said Senator John Kerry, the party’s 2004 nominee. “The choice is clear; our cause is just; and now is our time to make Barack Obama the next president of the United States.”

Mr Obama “can relate to the kind of struggles that people in America … are feeling right now”, said Senator Ken Salazar, a Colorado Democrat, while formally nominating Mr Obama as the party’s candidate.

Chants of “Obama, Obama” and “Yes, we can” surged up from the convention floor as speaker after speaker pledged support to the Illinois senator. Thousands of Democrats broke into spontaneous celebrations.

Hillary and Bill Clinton’s endorsement “seemed to melt away the tension and divisions of the past … and prepare the way for Mr Obama to take firm control of his own convention,” commented the Washington Post.

But not all agreed with this observation.

Earlier in the day, Mrs Clinton formally released her delegates, freeing them to vote for Mr Obama. But some of her delegates shouted “no, no” to her declaration.

“She doesn’t have the right to release us,” Massachusetts delegate Nancy Saboori told Associated Press. “We’re not little kids to be told what to do in a half-hour.”

And hundreds of delegates voted for Mrs Clinton in the roll call — 341 to Mr Obama’s 1,549 — before she called for him to be approved by acclamation. But none of this could diminish Mr Obama’s achievements.