A race between at least six rival developers and an all-out war between the National Press Club and the National Theater have been set off by the opportunity to develop two prime properties in downtown Washington.

The stakes are the vacant Willard Hotel and the block directly across 14th St. NW from it that is now occupied by the Press Club, and the National Theater and several stores and parking lots.

The Pennsylvania Avenue Development Corp. at the end of this month will accept proposals from the two sites, which are to be the cornerstones of the effort to revitalize the neighborhood.

Marriott yesterday became the third major developer to announce it would seek the Press Building block. Marriott proposed to build, with Quadrangle Development Corp., a $100 million complex with offices, stores and an 850-room hotel.

Atlanta architect John Portman in partnership with the Press Club and Washington's John Akridge Co. have already announced others for the same site.

Public bids for the neighboring Willard have been made by three more large builders - The Oliver T. Carr Co., The Radisson Hotels of Minneapolis and Trust House Forte of Chicago.

The competition turned into a confrontation yesterday when the directors of the National Theater endorsed the Marriott and Akridge proposals but refused to back the Portman Project.

The heart of the dispute is what will happen to the National Theater when the block is rebuilt.

Marriott's plans call for leaving the theater in its building at 1321 E St. NW., and building the hotel office complex around it.

Akridge would build a new theater in the center of the block behind the present one, and erect an office tower on the old theater site.

Portman once included a new theater in his plans, but recently has contended that is not ecnomically feasible and that the theater should be move to a new building on a nearby block.

Portman's proposal was described yesterday as "unrealistic, not well though out, you might even say half-based," by Roy Harris, a former National theater board member who is now a consultant to the group.

Harris complained that Portman's plan would tear down the recently refurbished theater, forcing the group to find a new home and raise $10 million to build it.

"We do not support that plan at all," said Harris, even though Portman has offered to help raise the money for a new theater.

The theater's board chairman, Maurice B. Tobin, issued a statement endorsing the Marriott and Akridge plans, saying they "prove that the National Theater can stay where it's been for 143 years and still allow dynamic, attractive and economically feasible development throughout the block."

That position produced equally unconciliatory responses from officials of the National Press Club, which owns about 77 percent of National Press Building.

The theater's "attitude has been that they'd like to have a new theater if we build it and pay for it," said Frank Aukofer, a Milwaukee Journal Washington correspondent who is president of both the Press Club and the Press Building Corp.

"No way are the Press Club and Portman going to spring for $5 million apiece to give them a theater," added Henry Keys, executive director of the Press Building Corp.

Aukofer said the club has made three proposals for including a small theater in the project an Portman volunteered to develop a nearby site including a new theater.

That proposal depends on the PADC donating land for the theater. PADC officials, however, say that the government corporation is supposed to foster development by private firms, not subsidize projects. PADC would have difficulty justifying the decision to give land to the theater when commercial developers are lining up to buy property nearby, officials said privately.

Portman's contention that a new theater could not be financially feasible in the project was challeged by Henry Bowden, the Akridge vice president in charge of the project.

Dismissing Portman's estimates that a new theater might cost $10 million, Bowden said Akridge puts the price closer to $4 million, an amount that could be absorbed by the $150 million complex.

By including the theater the developer gets a bonus in the size of building he can build under local regulations, Bowden noted. Utiilizing the interior of the block for the theater would allow construction of a profit-making office building on the present theater site.

Akridge's proposal is mostly an office complex, with 1 million to 1.35 million square feet of offices, 200,000 square feet of stores and possibly a 250- to 300-room hotel.

Yesterday's proposal from Marriott Corp. calls for an 850-room hotel, 450,000 square feet of office space and 100,000 square feet of stores in a three-level mall. Marriott would manage the hotel under a long-term contract. Marriott also would leave the theater in its present building.