Prospects dimmed yesterday for the expansion of Manassas National Battlefield Park when the Prince William County Board of Supervisors rejected a proposed compromise and demanded that the plan be killed.

The board's action leaves the fate of the plan in the hands of Sen. Harry F. Byrd (Ind-Va), who has kept a House passed bill to increase the park by 1,700 acres bottled up in committee while he waited for opposing sides in the controversy to resolve their differences.

A spokesman said yesterday that Byrd would have no immediate comment on the board's decision. Byrd has said in the past he would give "full consideration" to the local government's view.

The county board's 4-to-2 vote against the compromise came after a long Monday night hearing marked by-hostile exchanges between supervisors and Rep. Herbert Harris, the prime sponsors of the bill.

At a board work session yesterday afternoon, Supervisor Andrew J. Donnelly joined Supervisors Alice Humphries, Donald Wood and James Byrd to create a majority against the bill. James McCoart and Kathleen Seefeldt said that they believed a satisfactory compromise could be reached. Supervisor T. Clay Wood was out of town.

A vote by board members last night made their position official.

A National Park Service spokesman yesterday called the move "unfortunate" and Harris said, "We ought to be able to come up with positive solutions consistent with preserving historic areas. I think we owe it to the nation and our heritage to try to work constructively to preserve that area." "I'll wait to hear what the board says to the senator (Byrd). If the senator wants to hear my advice on preserving those historic areas while preserving the affected individuals' right I would be willing to give it," Harris said.

The Monday hearing, the first called by the board in the months the park bill has been in dispute, opened with James Byrd challenging Harris' presentation to the audience.

"Aren't we getting a little out of line with the congressman trying to convince the people?" said Byrd, who the proposed that the $8.5 million cost of the Harris plan be used to reduce sewer bills.

That, Byrd said, would be a "better memorial" to the Civil War dead whose "ancestors (sic) will be able to flush their toilets." Harris replied, "I sure like his (Byrd's) style." Byrd later stalked out of the hearing, complaining that nonresidents of the county were being allowed to speak.

The bill's supporters generally took a reassuring approach to the issue, contending that expansion of the battlefield would not hurt the county's tax structure or harm the park's neighbors or "in-holders," persons who own land within the park boundaries.

Opponents called it a federal "land grab," rejected Harris' attempts at compromise, and in the words of Duane T. Buryea, accused Harris, the Interior Department and expansion supporters of "a campaign of deception, delusion, deceivement, sham, and evasion."

Also yesterday, the Prince William board opposed full congressional representation for the District of Columbia, citing the danger of a commuter tax and "excessive" federal subhidies to the city.

The board rejected 4 to 2 the request from the Metropolitan WashingtonCouncil of Governments for support of the bill that has passed the House and is now in the Senate. The COG board is to consider the proposal today.