D.C. Mayor Anthony A. Williams said yesterday that he will try to build public support for a $440 million, city-financed baseball stadium project by stressing the economic and community benefits that a major league team could bring to Washington and assuring residents that businesses would be taxed to pay for it.

The District would pay all upfront capital costs for a stadium on the Anacostia waterfront. But Williams (D) and his aides said that they fought successfully to include free tickets for low-income children, to have the team owners pay millions in rent each year and to ensure that D.C. residents and minority contractors get priority consideration for jobs.

Williams said he was convinced that Major League Baseball officials, who have said they are very close to a decision on whether to move the Montreal Expos here, would have rejected a deal that did not include full financing.

"Do I think it's the ideal, optimal way to do business? No. . . . Of course, I would like some owner to come in and pay," Williams told a group of Washington Post reporters and editors. "But that's the reality of the sports world."

In a 90-minute briefing, Williams and his aides also shared details of the plan they are negotiating with MLB. The 41,000-seat stadium would be built just off South Capitol Street, a block from the Navy Yard Metro station. It would include 2,000 club seats, 74 luxury boxes and a 1,100-vehicle parking garage.

Parking revenue during baseball events would go to the team owner, but revenue on non-game days would go to the city, the officials said. The city would be able to stage six non-baseball events -- such as concerts or other performances -- at the stadium during the baseball season and six in the off-season.

Stephen M. Green, a special assistant to the mayor for economic development, said baseball owners quickly agreed to some aspects of the deal, such as substantial financial penalties and liabilities should the team stay in the District less than 30 years.

But the team owners were very reluctant to pay the rent the District asked for, Green said. Eventually they agreed to a 30-year lease with payments of $3.5 million the first year, increasing to $5 million by the fifth year and increasing by 2 percent each year after that.

"We have walked up to what we believed was the brink and looked over, several times," Green said. He said the city tried to retain the right to a premium that can be charged to customers who want tickets for the best seats -- but baseball owners would not agree.

City officials expect residents and tourists to flock to games if baseball returns to Washington after a 30-year absence and for attendance to stay strong for three to five years, even if the team struggles. They predict about 30,000 fans a game, or 2.4 million a season, which would be in the top third of the major leagues. Baseball officials have agreed to give away hundreds of tickets a game to low-income residents and to pay $1 into a community sports fund for every ticket above 2.4 million sold in any year.

Sports financing experts were mixed in their reactions to the package, which includes renovating Robert F. Kennedy Memorial Stadium for use while a new stadium is under construction. The bonds to cover the cost of the stadium would be repaid by the annual rent, taxes on tickets and concession sales in the stadium and a tax levied on businesses grossing more than $3 million a year.

David M. Carter, a Los Angeles-based sports consultant, noted that the plan places the financial burden on the shoulders of those who benefit, such as fans and the city's largest businesses.

But Chicago-based sports consultant Marc S. Ganis said the city's agreement to install refrigerators, stoves and other concession equipment could add as much as $35 million in cash to a package already beneficial for the new team owners. "If it's not the most favorable [in the nation], it's certainly close to it," Ganis said.

The financing would cover significant cost overruns, Green said. Revenue for the project should total at least $37 million a year, more than the $26 million debt service, he said. That means the debt could be paid off early, or that there would be enough money to make the payments even if ticket sales were slow.

Williams said he favored the South Capitol Street site because he believes a stadium there would significantly speed the pace of redevelopment along the Anacostia waterfront.

The stadium plan has caused an outcry from community groups, who say any additional tax revenue should go to schools and libraries. But business leaders have been supportive, saying their tax burden would be bearable and worthwhile.

Williams said he would work to convince residents that spending goals for schools and libraries were not in conflict with a stadium, saying he has steadily increased spending on schools and plans a major effort to overhaul libraries.

"There's a huge need on our part to promote this . . . so people understand that we're not taking this out of general taxpayer funds or from mom-and-pop businesses," Williams said. "I think it's a good investment for the city. I think it's a sound investment."