The proposed $300 million Techworld high-tech trade center in downtown Washington has become ensnared in a court battle after the collapse of efforts by Mayor Marion Barry to work out a compromise between the project's developer and preservationists.

Developer Giuseppe Cecchi said yesterday that the dispute already has imperiled financing for the project, which is a key element of the city's downtown redevelopment plans. But Cecchi expressed confidence that the massive complex, planned across from the Washington Convention Center, would be built.

Earlier this week Cecchi and historic preservationists filed lawsuits, asking U.S. District Judge William B. Bryant to settle their dispute after the negotiations in which Barry participated broke down.

At issue is Cecchi's plan, approved by Barry and the D.C. City Council, to build an enclosed six-story bridge over Eighth Street NW connecting Techworld's two structures.

Cecchi, developer of the Watergate complex two decades ago, said the bridge is necessary to make the new project economically feasible. However, opponents, led by the D.C. Preservation League and the Committee of 100 on the Federal City, say the bridge would destroy a historic vista that was part of the original L'Enfant plan for the nation's capital.

Ground was broken in late October on part of the project's two-square-block site, which is bounded by Seventh, Ninth, I and K streets NW. But so far only a massive hole has been excavated -- no construction has begun.

Cecchi went to court on Tuesday, stating in court papers that the groups' threats of a lawsuit, first made in October, already have "effectively precluded the commencement of Techworld's further development, construction, and leasing because lenders will not fund their loan commitments until this dispute is resolved and the Techworld developers cannot prudently commit equity money while the disputes are ongoing."

Robert A. Peck, president of the Preservation League, which filed its lawsuit several hours after the Cecchi suit, said the negotiations broke down because Cecchi was unwilling to reduce the height and the width of the bridge enough to gain his group's approval. "We still harbor the hope that a solution can be reached without following the legal process to its end," Peck said.

Participants on both sides said Barry hosted four of the negotiating sessions in his office and urged both sides to compromise. Kwasi Holman, executive director of the Office of Business and Economic Development, confirmed that the mayor took part in the talks but declined further comment.

The Techworld project is planned as a 12-story wholesale trade mart for high-tech industries, attached to an 800-room hotel.

In the suit, Cecchi asked Bryant for a declaratory judgment upholding the decision of the D.C. City Council in 1984 to close the block of Eighth Street between I and K streets, over which the Techworld bridge would be constructed.

The suit also asks for a declaration that under District law the building can be 130 feet high rather than the 110-foot height that preservationists say is legal.

The preservationists contend that the City Council had no authority to close the street because it is federal property and can be closed only by Congress.