Several congressional committees are considering ways to obtain the District's historic former main post office after a federal planning commission overwhelmingly rejected U.S. Postal Service plans to add 1 1/2 stories to the massive structure.

The political wrangling has added a new and complicated twist to the controversial project, which has been stalled since last Thursday's ruling by the National Capital Planning Commission.

In a 7-2 vote, the NCPC struck down the idea of a 33-foot rooftop addition, proposed by the postal service and its private New York development partners. The plans were part of an overall $100 million renovation of the 73-year-old Beaux Arts building at Massachusetts Avenue and North Capitol Street NE.

NCPC members who voted against the postal service measure sided with historic preservation groups in arguing that the proposed rooftop addition would destroy the architectural character of the building, as well as the vista of the surrounding area.

Within hours of last Thursday's vote, according to several Capitol Hill sources, various Senate and House committee staff members began contacting one another with news of the results, which they viewed as giving renewed impetus to congressional efforts to obtain the building.

"Congress feels it ought to have the first shot at the building," said David Sharman, staff director of the House Administration Committee. "It's in a bargaining situation."

Staff members of the seven committees involved in what were described as testy negotiations said several members of Congress are interested in obtaining the building for use as office, printing plant and warehouse space for both houses.

Several of the participants said options for the postal structure discussed so far have included purchasing the building from the postal service or leasing space in it if a revised development plan is approved at some point by the NCPC.

Postal service officials acknowledged the current Capitol Hill interest in the building.

"We could come back with another plan, we could sell it, convert it the way it is without the addition or we could appeal the {NCPC} decision," said Preston R. Tisch, the postmaster general, in an interview this week with a group of Washington Post editors and reporters. "We haven't decided yet."

He said a price for the building "has not been determined yet."

But the decision is not one necessarily to be made by the postal service.

"Congress has the authority to do whatever it wants. It is public property," said George White, architect of the Capitol. White has been described by various negotiators as one of the strongest backers of the proposal that Congress obtain the postal building.

Congressional interest in the building has been mounting the past couple of years, led notably by Sen. Wendell H. Ford (D-Ky.), chairman of the Senate Rules and Administration Committee, and Rep. Frank Annunzio (D-Ill.), chairman of the House Administration Committee.

"It is readily apparent that acquisition of this substantial building would be the most economical way of meeting the space requirements of the legislative branch," wrote Annunzio in a letter, which was obtained by The Washington Post, to Rep. James J. Howard (D-N.J.), chairman of the House Public Works and Transportation Committee.

When Annunzio's letter was written three weeks ago, it was becoming increasingly obvious to the various sides that the postal service project was in trouble.

After last week's NCPC ruling, congressional backing for obtaining the building "was renewed," White said.

This week, staff members of Ford's and Annunzio's committees, as well as those from the Senate budget and House public works committees and others, met with postal officials "just to talk" about the future of the building, according to one of those involved in the negotiations.

But postal officials said the meeting was more than casual.

"Their interest is serious," said Dennis Wamsley, real estate manager at the postal service, who was involved in the talks.

Asked what effect the negotiations could have on the postal service's plan to renovate the building, Wamsley said: "It could kill it."

One congressional staff member said the notion of Congress buying the building would face stiff opposition, especially when federal budget deficits are becoming an increasing political liability.

"This is an idea that died a few years ago, and, like Dracula, now it's coming out of the grave again," said one Senate Budget Committee staff member who attended this week's negotiations.

Postal officials and their private development partners expressed anger that Congress is now interested in the property. Wamsley said his agency was told last year that Congress was no longer interested in the building, except for possibly leasing space when it reopened.

"We viewed that as a green light to go ahead and do something with the building," Wamsley said.

Stephen Porter, a Washington lawyer representing the private developers, said his clients "spent a lot of money on the project {thinking} that Congress was not interested in the building."

He said the developers are still interested in renovating the building, which has sat mostly empty since the postal service moved the city's central mail handling operations to Brentwood Avenue NE last year.

"We are anxious to do the project, but obviously we can't control what happens on the Hill," Porter said.

In what had been chiefly an architectural dispute, the future of the building has become embroiled in a political tug-of-war with the various sides vying for a structure in an area of the city emerging as one of the hot development spots. As with most political tussles, charges were flying back and forth all week.

Before the NCPC vote last week, postal officials and representatives of the developers spent the past month heavily lobbying the various commission members -- a pressure tactic rarely seen in the past by the NCPC members.

This week, developers wondered privately what pressure was brought by legislators upon the NCPC, whose 12-member board includes two representatives of Congress.

Dietra L. Ford, an NCPC board member who represents Rep. Ronald V. Dellums (D-Calif.) on the federal planning panel, said she heard of no lobbying from congressional offices before the NCPC vote.

"We all reserved judgment on the project until it had a full hearing," she said.

Wamsley of the postal service said his agency still prefers to proceed with the project as part of a joint venture with the New York developers.

"But if we get the value {from Congress} for the building, and if we're going to have a difficult time with the NCPC, there is a scenario that the postal service wouldn't be harmed," he said.