NEW YORK (AP) _ The turmoil in China has turned what had been an increasingly popular destination for U.S. travelers into a canceled trip for many vacationers.

The bloody upheaval has prompted U.S. tour operators to cancel vacation packages to China and compelled airlines specializing in the Pacific region to re-evaluate their service to Chinese cities on a daily basis.

A number of operators, including American Express Co., said Tuesday they had decided to scrub tours to China. Tourism had been one of China's fastest- growing industries before the military crackdown in Beijing on pro- democracy demonstrators.

''We're looking at it on a day-by-day basis,'' said Lythia Rousseas, a marketing associate for Pacific Delight Tours in New York, considered the largest U.S. tour operator specializing in China and the Far East.

Customers have been promised full refunds, but may experience delays in claiming them from smaller tour operators, travel experts warned.

Travel companies continuing normal operations, such as United Airlines, are closely watching developments in China. ''We're continuing to monitor the situation,'' said Joe Hopkins, a spokesman for United at its Chicago headquarters.

The airline is operating a normal schedule of three flights a week between Tokyo and Beijing, he said. ''The flight yesterday had a very light load going in (to Beijing) - just five people. We had 307 going out.''

United has adjusted the schedule to minimize risks. The planes now arrive at Beijing in daylight, stay about an hour and leave; previously, they had an overnight layover.

Japan Air Lines has doubled its Tokyo-Beijing schedule by adding three flights a week, according to Morris Simoncelli, a spokesman for the carrier in New York. The flights out of Beijing are fully booked through Saturday, he said.

The State Department issued a new travel advisory Monday, warning Americans not to visit China and for those in Beijing to stay indoors. The department also urged caution in other Chinese cities.

On Tuesday, the Bush administration urged the 1,440 Americans in Beijing to get out, and said it was considering using chartered aircraft to evacuate Americans from the capital and other areas of the country.

American Express said its four tour groups currently in China - about 80 travelers in all - have been told to cut their visits short and leave the country immediately, said Marcos Rada, a company spokesman in New York.