WASHINGTON - Democratic Sen. Barack Obama of Illinois jumped into the 2008 White House race on Tuesday, promising to bring Americans together and "change our politics" with a campaign that could make him the first black president in U.S. history.

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 10.

"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," 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.

Obama, 45, is the fifth candidate in a Democratic White House field expected to be led by Sen. 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.

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.

Obama, who gave the keynote address at the 2004 Democratic convention before he was even elected to the U.S. 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 and about whether the United States is ready to elect a black to the White House.

In his statement, 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 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.

Obama"s quick rise has been fueled in part by his smooth campaign style and unusual personal history. The son of a white Kansas-born mother and a black Kenyan father, the Harvard Law School graduate and little known state legislator in Illinois won the U.S. Senate seat in 2004 against a stand-in opponent.

He has written two best-selling books and won a Grammy Award for his spoken word recording of his autobiography, "Dreams from My Father: A Story of Race and Inheritance."

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.

More Democrats, including Delaware Sen. Joseph Biden and New Mexico Gov. Bill Richardson, are expected in the race soon. While Clinton leads early polls of the Democratic field, Obama"s standing has risen sharply in the last few months.

Obama said he would spend the next few weeks listening to voters and learning about "the role that a presidential campaign might play in bringing our country together."

"A change in our politics can only come from you; from people across our country who believe there"s a better way and are willing to work for it," he said.