WASHINGTON, D.C. - Democratic Sen. Barack Obama on Tuesday took the initial step in a bid that could make him the nation's first black president.

Obama filed papers creating a presidential exploratory committee, a move he announced on his Web site, www.barackobama.com. He said he would announce more about his plans in his home state of Illinois on Feb. 10.

"I certainly didn't expect to find myself in this position a year ago," Obama said in a video posting. "I've been struck by how hungry we all are for a different kind of politics. So I've spent some time thinking about how I could best advance the cause of change and progress that we so desperately need."

Obama, a 45-year-old with little more than two years into his Senate term, is the most inexperienced candidate considering a run for the Democratic nomination. He quickly rose to national prominence, beginning with his keynote speech at the 2004 Democratic National Convention and his election to the Senate that year, but still is an unknown quantity to many voters.

Two best-selling autobiographies - "The Audacity of Hope: Thoughts on Reclaiming the American Dream" and "Dreams from My Father: A Story of Race and Inheritance" - have helped fill in the gaps but have still only touched a fraction of the public.

Nonetheless, he ranks as a top contender. His appeal on the stump, his unique background, his opposition to the Iraq war and the fact that he is a fresh face set him apart in a competitive race that also is expected to include front-runner Sen. Hillary Rodham Clinton of New York.

Other Democrats who have announced a campaign or exploratory committee are 2004 vice presidential nominee John Edwards, former Iowa Gov. Tom Vilsack, Connecticut Sen. Chris Dodd and Ohio Rep. Dennis Kucinich.

Obama's announcement was comparatively low-key, banking on the hype building up to his decision to drive the buzz rather than a speech or high-profile media appearance. He was in Washington on Tuesday but did not plan any public appearances.

Obama tried to turn his biggest weakness - his lack of experience in national politics - into an asset by criticizing the work of those who have been in power.

"The decisions that have been made in Washington these past six years, and the problems that have been ignored, have put our country in a precarious place," he said.

"America's faced big problems before," he said. "But today, our leaders in Washington seem incapable of working together in a practical, commonsense 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."

He said Americans are struggling financially, dependence on foreign oil threatens the environment and national security and "we're still mired in a tragic and costly war that should have never been waged."

Barack Hussein Obama was born in 1961 in Honolulu, Hawaii, where his parents met while studying at the University of Hawaii. His father was black and from Kenya; his mother, white and from Wichita, Kan.

Obama's parents divorced when he was two and his father returned to Kenya. His mother later married an Indonesian student and the family moved to Jakarta. Obama returned to Hawaii when he was 10 to live with his maternal grandparents.

Obama is a graduate of Columbia University and Harvard Law School, where he was the first African-American elected editor of the Harvard Law Review. He settled in Chicago, where he joined a law firm and taught constitutional law at the University of Chicago's Law School.

He also helped local churches establish job training programs for residents of poor neighborhoods and organized a major voter registration drive in the 1992 election.

While working at the corporate law firm Sidley Austin in the summer of 1989, Obama met Michelle Robinson, then an associate attorney at the firm. They married in 1992, and have two daughters, Malia and Sasha.

In 1996, he was elected to the Illinois state Senate, where he earned a reputation as a consensus-building Democrat who was strongly liberal on social and economic issues.

He backed gay rights, abortion rights, gun control, universal health care and tax breaks for the poor, but set himself apart from others by working with opponents to resolve policy disagreements and refusing to become a rubber stamp for his allies.

The retirement of Republican Sen. Peter Fitzgerald of Illinois in 2004 drew a raft of candidates to the Democratic primary, but Obama easily outdistanced his competitors.

He was virtually assured of victory in the general election when the designated Republican candidate was forced from the race by scandal late in the election. His GOP replacement - conservative gadfly Alan Keyes, who is also black - garnered less than 30 percent of the vote.

Obama insisted during the 2004 campaign and through his first year in the Senate that he had no intention of running for president, but by late 2006 his public statements had begun to leave open that possibility.

Last month, he traveled to New Hampshire, the first-in-the-nation primary state, and drew rock-star size crowds to a speech and book signing.

The 2008 presidential field at-a-glance

A year before the first primary votes are cast, the 2008 presidential field is already growing crowded. A list:

Democrats who have created exploratory committees:

Former North Carolina Sen. John Edwards

Connecticut Sen. Chris Dodd

Iowa Gov. Tom Vilsack

Ohio Rep. Dennis Kucinich

Illinois Sen. Barack Obama

Potential Democratic candidates:

Delaware Sen. Joe Biden (Has said he will run, but has not yet filed paperwork with the Federal Election Commission)

Retired Gen. Wesley Clark

New York Sen. Hillary Rodham Clinton

Former Vice President Al Gore

Massachusetts Sen. John Kerry

New Mexico Gov. Bill Richardson

Republicans who have created exploratory committees:

Kansas Sen. Sam Brownback

Former Virginia Gov. Jim Gilmore

Former New York City Mayor Rudy Giuliani

Arizona Sen. John McCain

Former Massachusetts Gov. Mitt Romney

Former Wisconsin Gov. Tommy Thompson

California Rep. Duncan Hunter

Texas Rep. Ron Paul

Colorado Rep. Tom Tancredo

Other potential Republican candidates:

New York Mayor Mike Bloomberg (also a potential independent candidate)

Former House Speaker Newt Gingrich

Nebraska Sen. Chuck Hagel

Former Arkansas Gov. Mike Huckabee

Former New York Gov. George Pataki