The District's attempt to bring major league baseball back to the nation's capital was thrown into uncertainty yesterday when D.C. Council Chairman Linda W. Cropp declared that she will pursue building a publicly funded baseball stadium adjacent to Robert F. Kennedy Memorial Stadium, breaking sharply from Mayor Anthony A. Williams's plan to build along the Anacostia River.

Cropp (D) made her announcement just four days before the council's key vote Tuesday on the future of the stadium. She shocked Williams (D) and her council colleagues by saying that the mayor's plan was too expensive and risky for the city's businesses that would be taxed to pay for construction.

It is not clear, however, whether either Cropp or Williams has enough votes lined up on the 13-member council to pass a plan. Both have four or five solid supporters, with the remaining members undecided or opposed to both proposals. The mayor vowed to continue his fight, saying he will make a public appeal Monday on the city's cable channel.

Building a stadium next to RFK would save the city at least 20 percent compared with Williams's preferred site in Southeast near the Navy Yard and South Capitol Street, Cropp said. The cost of the mayor's plan, estimated by his advisers at $440 million, could soar to $530 million or more, according to an analysis released last week by Natwar M. Gandhi, the city's chief financial officer.

"This is a better deal for the District of Columbia," Cropp said at a midday news conference at the John A. Wilson Building. "The business community said they are willing to support baseball, but not at any cost."

Cropp's proposal did not include another key provision of Williams's plan, a community investment fund worth up to $450 million that could be spent on schools and libraries and that would be made possible by economic development around his proposed stadium site.

Williams responded angrily at his own news conference an hour later, saying that Cropp's proposal could "blow . . . up" the deal he cut with baseball officials to bring the Montreal Expos to Washington in the spring. Under the agreement, the team would play at RFK for three years, then move to a stadium along the Anacostia in 2008.

"The dream of having a team is at risk; it is in jeopardy," Williams said. "I can't emphasize it enough, so I'm trying to raise the volume. We've worked for 10, 20, 30 years for this, and now it's in jeopardy."

Reaction from Major League Baseball officials was muted. They said they will give the mayor until Dec. 31 to work out an acceptable plan, as originally agreed. Some prospective ownership groups of the team said they thought that Cropp's plan would not automatically reduce the value of the franchise or tamp down bids.

John McHale Jr., baseball's executive vice president for administration, said league executives were not panicking.

"We struck a deal with the mayor, which provided that he had until December 31 to get legislation passed which effectuated the baseball stadium agreement," McHale said. "We are some ways from that date, so we are not going to get too excited at this point."

Cropp worked on her plan into the early hours yesterday. About 10 a.m., she presented it to a group of city leaders, including Williams and his top aides; council members Jack Evans (D-Ward 2) and Vincent B. Orange Sr. (D-Ward 5); and D.C. Sports and Entertainment Chairman Mark H. Tuohey. As of last evening, Cropp had not spoken to Major League Baseball officials.

However, Tuohey immediately telephoned Chicago White Sox owner Jerry Reinsdorf, head of baseball's relocation subcommittee, to inform him of Cropp's actions. Reinsdorf declined to comment publicly yesterday.

Texas Rangers owner Tom Hicks, a member of the relocation committee, said baseball officials "thought they had an understanding [with the District], and I think at this point it would be difficult to deviate from that understanding."

Asked if she would allow Major League Baseball officials to take the team to another city if they do not like her proposal, Cropp said yes. "I don't want baseball to leave, but I want to do what's best for the District," she said.

Cropp's plan would leave in place the financing structure of the stadium, with the money coming from a gross-receipts tax on the city's biggest businesses, a tax on concessions and an annual rent payment by the team. The team's rent, starting at $3.5 million a year and rising annually, would remain the same as it was under Williams's plan, but the gross-receipts tax would be reduced, Cropp said. Her plan would collect a total of $21 million in taxes a year, compared with about $26 million under the mayor's proposal.

For weeks, business leaders have debated the structure of the gross-receipts tax. Some said the fees were too high, particularly because the city would be responsible for any cost overruns at the stadium. If costs soared, business leaders feared, the gross-receipts tax would simply be raised to cover them. The reaction to Cropp's plan was mixed.

Brian Boyer, spokesman for the city's Chamber of Commerce, said that Cropp's proposal is a "step in the right direction. We hope that a less costly option is adopted so that business is not adversely affected by bringing a baseball team and stadium here."

But Len Foxwell, director of governmental affairs for the Greater Washington Board of Trade, said his organization believes the city should stick with the mayor's plan.

"We're quite concerned about the timing and context of Cropp's proposal," Foxwell said. "We have a carefully constructed deal on the table, and we're afraid this could undo it."

Cropp's announcement was particularly shocking to Williams because she, along with Evans, had been involved in the negotiations with Major League Baseball officials for months. Williams and Evans said they believed all along that Cropp was on board with the plan and would help sell it to other council members.

Evans, chairman of the council's Committee on Finance and Revenue, held a 16-hour public hearing on the mayor's plan and later amended it and sent it to the full council for Tuesday's vote. "I'm going to vote for my proposal," he said. "If my proposal gets overrun, then we'll see what happens."

Williams has said a stadium along the Anacostia would bring economic revitalization to a neighborhood that has been neglected. Building at RFK would not generate such development because it is isolated by a giant parking lot, he said. Baseball officials prefer the Anacostia waterfront site because it is more inviting to fans, he added.

"Council member Evans, the chairman [Cropp] and I made a commitment to baseball, and it was not a conditional commitment," Williams said. "If I make a commitment, I have to live up to it. Reneging on that would send a horrible message."

Council members Phil Mendelson (D-At Large) and David A. Catania (I-At Large) joined Cropp at her news conference. Kathy Patterson (D-Ward 3) and Carol Schwartz (R-At Large) said in interviews that they are generally supportive.

Council members Evans, Orange, Harold Brazil (D-At Large) and Sharon Ambrose (D-Ward 6) have been firmly in favor of the Anacostia waterfront site. Kevin P. Chavous (D-Ward 7) and Sandy Allen (D-Ward 8) have offered support of the mayor's plan but also raised concerns.

Adrian M. Fenty (D-At Large) said he will not support any plan that uses public funds for a stadium. Jim Graham (D-Ward 1), who opposed details in the mayor's plan, expressed concerns about Cropp's proposal yesterday.

Both sides predicted significant lobbying during the next few days. Williams acknowledged that competing for votes with Cropp would be "an uphill struggle." Cropp, who wields great influence, will also be doling out coveted committee chairmanships to her colleagues in January.

Meanwhile, civic activists have complained that public money should not be used for a stadium but rather spent on schools, libraries and recreation centers. In response, Williams proposed creating the community investment fund worth up to $450 million. Cropp said the investment package could be considered later as a separate bill.

Ed Lazere, co-leader of a group that opposes using public money for a stadium, said he was glad that Cropp was trying to bring down the price of the stadium but said that his group will keep pushing for a major reduction in public funds for the project.

"This is the start of a renegotiation of a bad deal," Lazere said.

Williams and others feared baseball officials will reopen their own negotiations -- with other cities and regions that competed for the Expos, including Northern Virginia.

"Major League Baseball made its choice with D.C. We hope they are able to perform on their deal," said Keith Frederick, chairman of the Virginia Baseball Stadium Authority. "But should they not, we plan to be in a position to save the franchise for the area."

Staff writers Thomas Heath, Michael Laris and Lori Montgomery contributed to this report.

D.C. Council Chairman Linda Cropp said her alternative financing plan will be less of a burden on business. A satellite photo shows RFK Stadium in the top right. The new proposal calls for a ballpark adjacent to the stadium site instead of near the Anacostia River.