District officials, alarmed by signs of a downturn in visitors and reports of tour cancellations, have sought congressional help in countering nationwide perceptions that the Persian Gulf War has made the capital unsafe.

Attendance at the museums of the Smithsonian Institution was down more than 100,000 in January compared with the same month of 1990 and 1989, while visits to the Washington Monument and the Lincoln and Vietnam Veterans memorials dropped 12 percent.

Moreover, several hotel managers, tour bus operators and tour guides said they have begun receiving cancellations for the usually crowded cherry blossom season. Tourism officials added they understand that many tourists believe Washington's most popular attractions have been shut down because of a threat of terrorism.

The officials said the recession might be causing some visitors to stay at home, and the District's tourist image already was battered by its homicide rate and the trial of former mayor Marion Barry. But they attributed part of the loss to fears of war-related terrorism, which has reduced travel around the world but poses a particular burden for the District because tourism is the second-largest employer after government.

The officials said they were especially worried by reports that aides in some congressional offices have told constituents to avoid the District.

That prompted Del. Eleanor Holmes Norton (D-D.C.) to send a "Dear Colleague" letter on Jan. 31 to all 535 senators and representatives promising them that the city is "entirely safe."

But Norton's letter did not reach Rep. Jim Cooper (D-Tenn.) before he advised constituents in a news release to stay home, noting that "everyone knows that Washington, D.C., would be a prime target for terrorist bombings because of the large number of tourists and public officials."

"My best advice for Tennessee school groups is, for this year, please consider a different trip," Cooper wrote, adding that his constituents should "visit places in Tennessee where you've never been before."

An aide to Cooper said he was not aware of any tour groups cancelling their plans because of the congressman's statements, which were front-page news in the Knoxville News Sentinel.

The District's Convention and Visitors Association issued a news release announcing that, except for the White House and the Pentagon, the capital's attractions were open for business as usual. It also said that a visit to the capital would show support for the federal government.

"There are increasingly some very strange rumors that snowballed," said Tom Murphy, a spokesman for the association. "People think the city is shut down. When the White House closed for tours, that became a symbol for the whole city. We are frantically fielding all these calls about spring trips. The wildest one was bad but comical. I had someone calling from Iowa who says he had heard the federal government had banned all travel to the nation's capital."

As evidence that security is effective, Norton pointed to the State of the Union address, during which President Bush, the Cabinet, the Supreme Court and Congress all gathered safely on Capitol Hill.

But televised images of the strict security measures for the address sent a different message to some, who thought they signified Washington is unsafe.

Among those who will not be coming to see Washington at its springtime prettiest are 120 students from St. John the Baptist Junior High School in Cincinnati.

Their leader, Sister Elizabeth, said they canceled reservations with Delta Air Lines and the Holiday Inn on C Street SW because she was convinced terrorists would stalk her group and because she got the impression from the media that sites were closed.

"I am afraid to come," Sister Elizabeth said. "I know there are drugs and crime in Washington, but the only thing bothering us is the war. We are worried about attacks against tourists."

Girl Scout leader Cheryl Milot, of North Attleboro, Mass., said she will not bring her 12 scouts to the District in April because the place they want to see the most, the White House, is closed. She said parents also are concerned that Washington might be bombed.

Smithsonian Institution spokeswoman Madilyn Jacobs, while cautioning against drawing conclusions from data for only a few months, said January attendance appeared to be roughly normal on weekends. Washington area residents, who presumably know conditions in the city better, generally come on Saturday and Sunday, she said.

But attendance was down on weekdays, when out-of-town visitors and school groups usually come, Jacobs said. She also said that despite the recession, Smithsonian attendance was up in November and December, before the war began.

Sandra Alley, a spokeswoman for the National Park Service, said that although attendance at the Lincoln and Vietnam Veterans memorials and Washington Monument generally had been up in recent months, it dropped at all three sites in January.

She also said the Frederick Douglass home in Anacostia, which many school groups usually visit in February during Black History Month, probably will have a 30 percent decline this month.

Danny Harlow, owner of Sunshine Tours and Guide Service in Washington, said his business has been hit hard by cancellations for the spring.

"I am seeing a 75 percent fallout over last year," he said. "We had a full calendar for March and April, but now we are wide open for the Cherry Blossom Festival."

Faced with such widespread fears among her clients, Mona Wickner, who handles student tours to Washington from New York, said she is trying to persuade her groups not to cancel by giving them extensions on the dates for deposits and for full payment.

"Saddam has won in a way," she said. "He has people afraid, afraid to travel, afraid to be near a national monument. One teacher told me to find her a perfectly safe place for her students. She said to find a farm to visit in New Jersey."