D.C. Mayor Anthony A. Williams said last night that he will announce to supporters today that after seven years in office he will not seek a third term.

Williams, who had been hounded all day by the media, begrudgingly told The Washington Post of his decision while attending a dinner at the Ronald Reagan Building and International Trade Center.

"I'm announcing I'm not running. I'm telling you that," Williams said. "People have already said this. I don't want to say anything more."

He plans to explain his decision at noon today at a recreation center in the Hillcrest neighborhood of Southeast Washington, where local activists drafted him to run for mayor and ignited his political career.

The mayor's decision has been anticipated for months. Some of his supporters started joining the campaigns of other candidates after he failed to contact them or begin raising money for reelection.

In recent months, Williams has hinted that he would not run, saying that his wife, Diane, is eager for him to retire from public life and that, at 54, he is ready for a more lucrative job in the private sector. At a luncheon with Post reporters and editors in April, he said he might not have "the energy, the tenacity, the discipline, the focus" to serve a third term.

"You really should not do this job unless you're willing to put in that enormous amount of effort," he added. "You should not do the job unless you're willing to take risks. And you shouldn't do the job unless you're willing to lose the job, too."

Williams has nonetheless dodged questions about his political future. A source close to the mayor said last night that Williams has finally decided that it's time to release his supporters to sign on with other candidates.

So far, the 2006 race for mayor has drawn five Democratic contenders, including D.C. Council chairman Linda W. Cropp, council members Adrian M. Fenty (Ward 4) and Vincent B. Orange Sr. (Ward 5), lobbyist Michael A. Brown and former telecommunications executive Marie C. Johns. With Williams officially out of the picture, the candidates will wage an aggressive campaign to pick up endorsements and cash from former Williams loyalists.

Many of Williams's staunchest supporters have said they are not inclined to back any of the current candidates for his job, citing in some cases a lack of experience and in others a lack of vision.

"I hope we get somebody who has proven themselves, at least, in a tough job," said Max N. Berry, co-chair of Williams's 2002 reelection campaign.

If nothing else, Williams has proven over the past decade that he could handle the tough jobs. He joined local government in 1995, when then-Mayor Marion Barry appointed him to serve as chief financial officer of a city the General Accounting Office had declared insolvent. Drafted to run for mayor in 1998, Williams won -- and inherited a boarded-up, trash-strewn downtown along with a dysfunctional city bureaucracy that still used rotary phones, couldn't manage to collect people's garbage and operated at the whim of a federally appointed control board.

Williams quickly brought an air of competence to the District Building, balancing city budgets and releasing Washington from control board authority. He also attracted development downtown and to neighborhoods across the city, while pushing for radical changes in the urban landscape, including redevelopment of the Anacostia waterfront and renewal of the city's historic thoroughfares.

Many supporters said they would be disappointed if Williams did not run.

But Rock Newman, a boxing promoter and early Williams supporter, said: "If he decides not to run, I definitely respect that decision. As far as I'm concerned, he's done an extraordinary job. The balancing act of developing a city and attracting business ... being able to have a positive impact on the underprivileged while trying to tap dance and juggle without having the economy of a state -- it's a hard job."

Throughout the summer, many supporters waited for a sign from Williams. But in recent weeks, as two candidates entered the race for his job and a third held a citywide campaign kickoff, Williams left town for a 12-day trip through Europe.

Upon his return last week, rumors swirled that he was finally ready to make an announcement.

Anthony A. Williams's decision not to run ends months of speculation.