Washington and Baltimore will make an unprecedented joint bid for the 2012 Olympic Games, organizers are set to announce today, hoping to resolve a bitter behind-the-scenes battle over the right to lead an effort that could bring billions of dollars to the region.

Washington Mayor Marion Barry and Baltimore Mayor Kurt L. Schmoke each will appoint as many as five board members to join a dozen executives from some of the region's largest companies, including Mobil, Bell Atlantic and NationsBank, on a new consolidated organizing committee. Each executive has pledged $500,000 for a seat on the board and for an opportunity to gain the inside track on future service contracts associated with the Games.

Olympic handicappers have given the newly created Washington Baltimore Regional 2012 Coalition a fighting chance to beat out such U.S. contenders as Houston, New York City and Seattle and international bidders including Cairo, Johannesburg and Beijing.

Indeed, Olympic officials said that by pooling their resources, the former rival cities have helped their cause to become the fourth American host for the Summer Olympic Games.

"There's no downside," said Mike Moran, a spokesman for the United States Olympic Committee, which will select its candidate for host city in 2002. "It's impressive that two great American cities have done this."

As part of the deal, business leaders succeeded in keeping the chairman of Washington's Olympic exploratory committee off the new board. Elizabeth Ganzi, whom Barry once praised as the inspiration behind Washington's 17-month effort to win the Games, threatened yesterday to file suit against the combined committee.

Moran said the USOC would focus on the bid authorized by Barry, and the mayor on Friday sent a letter to the USOC calling the joint committee the District's "sole and exclusive" representative in the worldwide contest for the Games.

"The people who could put some money up said we want this to be as regional a bid as it could be," said Barry, who previously supported the Ganzi-led Greater Washington Exploratory Committee. "Politically, it doesn't make sense for me not to support a regional bid. Plus, this just makes more sense."

In December, regional business leaders met in Howard County to discuss joining Baltimore and Washington in a single bid that could cost $30 million.

If the region is picked by the USOC, one city will take the lead role in competing before the International Olympic Committee. Barry said yesterday Washington would be that city. The IOC is scheduled to select a host city for the 2012 Games in the fall of 2005.

An ambitious Washington promoter, Ganzi was supportive of early discussions to merge the efforts of the two cities in the belief she would have a seat on any future board. But she alienated several business leaders when the USOC questioned whether she had engaged in improper lobbying during this year's Nagano Games. Executives from NationsBank Corp., Mobil Corp. and others threatened to pull out of the joint bid if Ganzi were named to the board, according to members of the combined bid.

In an interview yesterday, Ganzi accused joint bid organizers of squeezing her out of a process she started, leaving her organization about $200,000 in debt. Ganzi has raised roughly $1.5 million in cash and in-kind contributions since forming the Greater Washington Exploratory Committee with Barry's blessing last year.

"This was never about mayors and big businesses winning bids," Ganzi said. "It was about an individual with a vision. It's about fair play. It's about unity."

Today is the deadline for bid cities to submit proof to the USOC that they have formed a committee with legal, nonprofit status. Ganzi said the Greater Washington Exploratory Committee filed its own committee paperwork with the USOC, essentially setting up a competition between the regional bid and a Washington committee that now has five board members.

Ganzi's break with Barry, who said "Elizabeth is not cooperating," marks a significant turnabout from just a few months ago, when Ganzi, from her cellular phone courtside at the Monte Carlo Open tennis tournament, rallied Barry to make media calls on her behalf. He did. But yesterday, Ganzi dismissed Barry, who will name four board members at today's event at Loews Annapolis Hotel, as a lame duck.

"If anyone says we don't have the right to represent Washington, there will be a lawsuit," said Terence P. Ross, an attorney for the Greater Washington Exploratory Committee. "We've got the inside track on this and we're blowing it."

Members of the new organizing committee are more optimistic. In addition to the eight members that will be appointed today by Barry and Schmoke, the combined committee will include William L. Collins, president of Metrocall Inc.; Marie Johns, Bell Atlantic Corp. president of District operations; Mary Junck, president of Times Mirror Eastern Newspapers, which owns the Baltimore Sun; Hugh Long, Washington area president of First Union Corp.; Pete L. Manos, chairman of Giant Food Inc.; Chip Mason, chairman of Legg Mason Inc.; John Morton, president of NationsBank's mid-Atlantic division; Robert Flanagan, vice president for Clark Enterprises Inc.; John Schwieters, managing partner for Arthur Andersen & Co.; Susan Williams, a principal in the Bracy Williams political consulting firm; George Stamas, partner in the Wilmer, Cutler & Pickering law firm; and Bob O'Leary, Mobil's general manager for public affairs.

The new bid is "collectively the best we have to offer," O'Leary said.