Travel to the United States from Japan and Europe has dropped dramatically since the Persian Gulf War began, according to a Commerce Department survey of travel-related firms in those foreign countries.

About a quarter of 100 companies surveyed reported they had suffered declines of 40 percent to 60 percent in tourism. Only 3 percent reported no impact.

Many Washington-area hotels and tour companies are feeling the pinch as foreign tour groups cancel reservations. The businesses also are suffering because Americans, fearful they will encounter terrorism, demonstrations or "closed" signs on monuments, are opting to stay away as well.

The slowdown in arrivals from abroad threatens to halt a steady increase in foreign travel to the United States that began in the 1980s. Many economists have hailed that boom, which brings dollars into the United States, as a crucial way for the country to offset its enormous trade deficits.

The Commerce Department yesterday reported that foreigners made 40 million trips (up 9 percent) to the United States last year and spent $53 billion (up 19 percent). This was about $5 billion more than American travelers spent abroad, giving the United States a surplus in this form of trade.

Breaking with past practice, the department declined to forecast levels for 1991. "The clouds of smoke over the Middle East have obscured my crystal ball," said Harvey Shields, acting director of research at the U.S. Travel & Tourism Administration, the Commerce Department's travel promotion wing.

Shields said he expected the United States to continue to enjoy a surplus in travel spending, however. If the war means that fewer foreigners will visit the United States, it probably also will mean fewer Americans will be going overseas.

The D.C. area's travel industry had already been hit by the city's reputation as the "murder capital" and a recession-related sag in business. Now comes the war and more cancellations, most of them from tour groups. The J.W. Marriott Hotel downtown has lost about $80,000 in tour group business for the first quarter due to the war, Greg Deininger, the hotel's marketing director, said yesterday.

In the belief that ignorance is causing many cancellations, the local travel industry is spreading the message through phone calls and meetings that life continues as normal in the area and is especially safe because of heavy security precautions, plentiful police officers and experience.

D.C. Mayor Sharon Pratt Dixon spoke out on the subject recently. And Del. Eleanor Holmes Norton circulated a letter to members of Congress, asking them to assure constituents that conditions are "entirely safe" in the District.

Still, the calls come in. "We talked to a lady from Iowa the other day and she said she heard from her 10 o'clock news that they had closed all of the tourist attractions and all of the monuments of Washington," said Dan Mobley, executive vice president at the Washington, D.C., Convention and Visitors Association. In fact, he said, only the White House and Pentagon are closed.

The Commerce Department survey, conducted last week, found that 24 percent of the surveyed firms reported their business of sending people to the United States had declined by up to 20 percent; 37 percent said it was down 21 percent to 40 percent; 23 percent reported a 41 percent to 60 percent drop; and 12 percent said it was down 61 percent or more.

Rockwell A. Schnabel, who heads the travel administration, said yesterday that he believed travelers were overreacting. . He said now was in fact a good time to travel. Security precautions are high and "very few people are traveling {so} you can get all sorts of deals," he told reporters.