The National Park Service is planning, for the first time in 11 years, to include a nativity scene in the federally sponsored Christmas Pageant of Peace, the annual holiday celebration that takes place alongside the national Christmas tree on the Ellipse.

Under pressure from a McLean religious group, the park service and the committee of citizens who oversee the pageant decided last summer to include a nativity scene in the pageant, a spokesman for the service said yesterday. The agency is working out the details of the display -- including where it is to be located in the pageant.

The annual display usually draws thousands of visitors to the park, located south of the White House, said spokesman Earl Kittleman.

Pressure for the nativity scene, he said, has come from a group called the Citizens for God and Country, a Northern Virginia organization that advocates including religion in national celebrations.

The Supreme Court ruled in March that the nativity scene is a cultural symbol, such as Santa Claus, and therefore doesn't constitute an unconstitutional government preference for Christianity. That ruling effectively overturned a 1973 decision by a U.S. district court of appeals, which directed the park service not to include a creche as part of the pageant's official program.

Every year since 1973, the National Park Service has granted a private group, called the American Christian Heritage Assocation, a demonstration permit for a life-sized nativity scene in the President's Park on the 15th Street side of the Ellipse. That display, however, has not been considered part of the government's program.

Arthur Spitzer, legal director of the American Civil Liberties Union for the Washington area, said last night he was troubled by the park service decision. "We think it's wrong," he said. "It's impossible for us to view that as anything but a government endorsement of Christianity, and that violates the Constitution."

Spitzer said that his group is considering challenging the decision in court, if it decides the action is not consistent with the Supreme Court ruling.

Spokesmen for the McLean group that lobbied for the nativity scene could not be reached for comment last night, but Sandra Alley, a park service spokeswoman, said the agency's lawyers reviewed the Supreme Court ruling before the service agreed to include the scene.

In a 1980 interview, Anne Neamon, founder of Citizens for God and Country, said she was the only member of her group, although she frequently said that she was speaking for thousands of people. At the time, she was fighting an effort to expand Fairfax County's sex-education program in the public schools.

She said then her group, whose address was a McLean postal box, was self-financed and she was the group's national coordinator.

The private group that has been staging the nativity scene near the Ellipse also could not be reached for comment last night. Vaughn Barkdoll, Prince George's County director of public works, had led the volunteer effort to include the scene, which costs about $5,000 to stage.

In an interview last year, Barkdoll said he was outraged in 1973 when the nativity scene was banned. "I just figured that a Christmas celebration without the creche and the true meaning of Christmas was a little bit ridiculous and somebody ought to do something about it," he said then.

His effort was supported by volunteers from the Knights of Columbus in suburban Maryland and others who would continually stand watch over the scene's live burro, calf and two sheep to prevent vadalism.

The same issue arose this week in Charlottesville, but with a different result. The City Council in that Virginia community, for the first time in 31 years, decided to ban a nativity scene from a downtown public park, saying the display violates the Constitutional mandate separating church and state.

Charlottesville Mayor Frank Buck said yesterday the City Council disagreed with the Supreme Court's ruling. "We're just simply saying it should not be on public property because it the nativity scene is a religious symbol," he said.

"It seems to me that in the Christian religion, there can't be many more things that are more holy and more sacred than the birth of Christ," he said.

Charles Burton, president of a Junior Chamber of Commerce group which had operated the scene, said his group doesn't want to argue and will move the scene elsewhere. "It just doesn't seem like it would be in the spirit of the holidays to get . . . stirred up about it," he said.