Democratic Senator Barack Obama of Illinois leapt into the 2008 White House race today, promising to bring Americans together and "change our politics" with a campaign that could make him the first black president in US history.
Mr Obama, a freshman senator and rising party star, formed a committee to begin raising money and hiring staff to campaign for the Democratic presidential nomination to succeed Republican President George W. Bush.
He plans a formal campaign announcement in his hometown of Chicago on February 10th.
"Our leaders in Washington seem incapable of working together in a practical, common sense way. Politics has become so bitter and partisan, so gummed up by money and influence, that we can't tackle the big problems that demand solutions," Mr Obama said in a video message announcing his bid.
"We have to change our politics, and come together around our common interests and concerns as Americans," he said.
Mr Obama, 45, is the fifth candidate in a Democratic White House field expected to be led by Senator Hillary Rodham Clinton of New York, who has not said whether she will try to become the first woman president but has promised an announcement soon.
Mr Obama's candidacy has stoked enthusiasm among Democrats looking for a fresh-faced alternative to Clinton, who some fear could be too polarizing to win a general election campaign against a Republican next year.
Mr Obama, who gave the keynote address at the 2004 Democratic convention before he was even elected to the US Senate, appeared on a Time magazine cover and drew big crowds while campaigning for Democrats last fall.
His visit to the early primary state of New Hampshire in December drew sold-out crowds and more than 150 journalists.
But the first-term senator also has been dogged by questions about his lack of experience.
In his statement, Mr Obama said he was struck by the hunger around the country for "a different kind of politics" and that decisions in Washington over the last six years of Republican leadership have put the country "in a precarious place."
"Our continued dependence on oil has put our security and our very planet at risk. And we're still mired in a tragic and costly war that should have never been waged," said Mr Obama, an opponent of the invasion of Iraq.
"But challenging as they are, it's not the magnitude of our problems that concerns me the most. It's the smallness of our politics," he said.
The other Democrats in the race so far are 2004 vice presidential nominee John Edwards, former Iowa Gov. Tom Vilsack, Ohio Rep. Dennis Kucinich and Connecticut Sen. Chris Dodd.