The restoration of the historic Tivoli Theater in Columbia Heights -- abandoned and empty since 1976 -- should begin in late April, D.C. officials and the developer said yesterday, after announcing an agreement that allocates $8 million in city funding to the long-awaited project.

Progress had stalled for the last 18 months as the developer, Horning Brothers, negotiated with D.C. officials and local preservationists over how much of the theater would be restored to its original glory, and who would pay the hefty tab for that work.

There were many other delays, stretching back decades, in rehabilitating the crumbling building, which occupies a prominent spot along the rapidly developing 14th Street corridor, at Park Road NW.

Tivoli Square, which is to include a restored theater as well as shops, offices, a new Giant Food supermarket and 40 duplex condominiums, is one of 10 planned developments in the span of a few blocks that could transform an area blighted since the riots of 1968.

"When this is restored, generations of Washingtonians will appreciate it," said D.C. Council member Jim Graham (D-Ward 1), who represents the area and has lobbied vigorously for the project. "Is it costing the city something? Yes. Is the city going to get something very, very substantial in return? Yes, absolutely."

Horning Brothers had said it needed $8.9 million from the city to fulfill an agreement to restore parts of the theater's interior, as well as the entire exterior. Deputy Mayor for Economic Development Eric W. Price, as recently as Jan. 8, had said the city would not pay more than $6.4 million.

But with time running out in the exclusive rights agreement that Horning Brothers negotiated with the city, and with Columbia Heights residents increasingly frustrated after hearing construction would start last summer, last fall or this winter, Price upped his offer by $1.6 million and the developer agreed to pay the rest.

Stephen M. Green, a top official in Price's office who helped negotiate the deal, said it is contingent on construction starting within 30 days after a land disposition agreement is executed, likely in the third week of March.

"We were, frankly, very concerned about the commencement of the work," Green said. "One of the things we've done is put a little extra money on the table to ensure that this will get done, soon."

Horning Brothers applied for construction permits yesterday and is ready to proceed when it gets necessary approvals, said Sean Cahill, chief operating officer.

About 60 days after construction starts at the theater, Cahill said, crews will begin work on the supermarket. The condominiums will be built after the commercial projects are complete.

"Our gears are in motion," Cahill said. "We're as frustrated as the community is."

Columbia Heights residents have vocally opposed delays in the project, and residents said yesterday that while they were glad the impasse was resolved, they would put off celebrating until construction begins.

"People will be delighted, but I think they will wait to see until some dirt turns over," said Elizabeth McIntire, the area's advisory neighborhood commissioner. "We'll believe it absolutely when we see it."

Washington developer Herbert Haft proposed turning the space into a Safeway in the 1980s and signed an exclusive rights agreement that languished for 15 years while preservationists sued to stop the proposal.

The site is now controlled by the District's National Capital Revitalization Corp., a quasi-public development entity that last year took it and other abandoned 14th Street parcels over from the now-defunct Redevelopment Land Agency.

Diagonally across 14th Street is an empty lot controlled by GRID Properties, which has proposed a major urban shopping and entertainment center anchored by a Target store. The NCRC last week approved a land disposition agreement that gives GRID until June 2004 or January 2005 to close that deal.

Most of the other planned projects involve apartments built over first-floor retail space.