A day before he formally accepts his party's nomination, Barack Obama has celebrated his history-making accomplishment.

Obama dropped in on the Democratic National Convention just after the party's vice-presidential nominee, Joe Biden, made an acceptance speech.

Obama asked the delegates to help him ``take back America'' in the fall campaign against Republican Senator John McCain of Arizona.

Like Biden, Obama was nominated by acclamation.

Former rival Hillary Rodham Clinton asked the convention hours earlier to interrupt its roll call of the states and make its verdict unanimous.

Bill Clinton has offered a ringing endorsement of Obama, saying Obama is ``ready to lead America and restore American leadership in the world.''

Clinton, who received a long ovation from delegates at the Democratic National Convention, told them he wants those who supported Hillary Clinton to vote for Obama in November.

The two-term former president said that with Obama's ``proven understanding, insight, and good instincts'' and Joe Biden's ``experience and wisdom,'' America will have the national security leadership it needs.

Clinton likened Obama's presidential quest to his own bid for the presidency in 1992, when Republicans said he was too young and too inexperienced to be commander in chief.

Clinton said it didn't work then and won't work now because ``Barack Obama is on the right side of history.''

Obama is now one victory from becoming president of a nation where, just decades ago, many blacks were denied the vote.

A campaign spokesman says Obama's acceptance speech Thursday will draw stark but respectful contrasts with McCain.

The address will be given before tens of thousands at Denver's Invesco Field at Mile High.

Addresses Thursday address will focus on Barack Obama's acceptance speech.

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