"We're going to run a campaign that will move this country forward not back," Clark said, promising to "talk straight to the American people."
Clark, 58, became the 10th Democrat in the race, joining a contest that has been under way for months.
"My name is Wes Clark. I am from Little Rock, Arkansas. And I am here to announce that I intend to seek the presidency of the United States of America," he began.
Clark has no experience in elective office and no history on domestic policy. But he offers Democrats one thing they crave: New hope of undercutting President Bush's wartime popularity.
Clark immediately took aim at the president, saying his economic policies "have cost us more jobs than our economy has had the energy to create."
Nearly 3 million U.S. jobs have been lost since Mr. Bush took office in January 2001. Clark vowed to "restore the millions of jobs that have been lost."
A critic of Mr. Bush's policies in Iraq, Clark also said that, "More than 100,000 American troops are fighting abroad and once again Americans are concerned about their civil liberties."
The former Vietnam veteran and commander of all NATO forces in Europe ended his speech by telling supporters, "Get ready. We're moving out."
Clark made his announcement at a boys and girls club in the state capital, under clear blue skies and on a small stage bearing a sign of his Web site: "americansforclark.com."
Supporters waved American flags and "Draft Clark" signs while volunteers passed out "Clark" chocolate bars to an audience of several hundred.
Fellow Arkansas Democrat Sen. Blanche Lincoln said in a statement that Clark "offers strong, tested leadership on critical challenges that confront our nation."
But with only four months to go to the first nominating contest, the political novice has a lot of ground to make up.
"Gen. Clark's appeal is based more on his military background," Congressional Quarterly's Craig Crawford told CBS News' The Early Show. "He doesn't have any expertise in handling the budget or any of the economic issues that will be central to the campaign so he's got some real liabilities there."
What Clark lacks in experience, he hopes to make up for in political firepower, reports CBS News Chief White House Correspondent John Roberts. He has recruited a company of Clinton-era lieutenants, including 1992 campaign chief of staff Eli Segal, Bruce Lindsey and Skip Rutherford.
Their presence suggests that while the former president has not given Clark his endorsement, he may have Mr. Clinton's blessing.
"He's provided advice and he's talked to me on several occasions," Clark said.
Some political watchers are wondering if there might be something more to this Clinton connection.
"Hillary Clinton has been rumored to be thinking of running for president," points out CQ's Crawford. "Would she be his running mate? Would he be her running mate? These are all questions that the chattering class will ask."
Clark's resume is made to order to take advantage of Mr. Bush's vulnerability on the economy and Iraq — a Rhodes scholar, first in his 1966 class at West Point, White House fellow and head of the U.S. Southern Command and NATO commander during the 1999 campaign in Kosovo.
However, the retired general has never held political office — not even a student council election to his credit, and just four months before the first votes are cast, he has no formal organization in key states, little money and a patchwork staff.
Clark's advisers said they are developing an unconventional strategy that would attempt to capitalize on the Internet and Clark's affinity for television — he's a regular on cable news shows — to build momentum nationwide.
He has not decided how hard to campaign in traditional early battlegrounds such as Iowa, aides said, but they quickly concluded that he can't catch up to his competitors through traditional means; the rest of the field has been in Iowa and New Hampshire for months.
Democrats in New Hampshire, Iowa and other early voting states did not close the door on a Clark presidency, but said the compressed primary schedule hurts late-starting candidates.
"While General Clark has something to say, it's going to take boots on the ground in Iowa to make a difference," said Iowa activist Joe Shannahan.