Shippers are increasingly nervous at the prospect that independent truckload operators will follow through with a threatened shutdown next week.

The owner-operators constitute 15 percent of the nation's 2.6 million truckers and haul one-third of the nation's inter-city truck freight, including a large portion of foodstuffs."Of course we're worried," said John F. Baxter, manager of distribution and customer service at Allied-Signal Inc. in Morristown, N.J. "This is right in the middle of the Christmas shipping season, and there's spot shortages of trucks all over the United States, especially on the West Coast."

For three weeks, a series of fliers have circulated at truck stops across the United States and Canada urging truckers to shut down trucking operations Nov. 11-17.

Owner-operators, estimated at 350,000, are furious over a litany of complaints ranging from a sharp rise in diesel fuel prices, impending competition from Mexican truckers under the North American Free Trade Agreement and what they believe is discriminatory harassment from state police.

Anger has been building since late September when truckers began a series of rolling blockades in Ohio and Indiana, said Todd Spencer, executive vice president with the Owner Operator Independent Drivers Association. The Grain Valley, Mo., group is monitoring, but not endorsing any job action.

The timing of the planned strike, a week before Thanksgiving, couldn't be worse for food receivers who are rushing to fill supermarket shelves and industrial manufacturers who use just-in-time raw material deliveries.

"Some of our customers are stepping up and making early buys of perishables that can be stored a while, like celery and carrots," said Peter Romero, general sales manager for D'Arrigo Bros Co., a Salinas, Calif., produce grower.

The crush is compounded by a driver and equipment shortage.

"Every truckload carrier I talk to is turning down freight," said J. Terry Turner, executive director of the Interstate Truckload Carriers Conference in Washington. "They don't have the equipment, and they don't have enough drivers to move the freight and they're being very selective about whose freight they're moving."

Many traffic managers are rushing to get freight delivered this week before any stoppage stops supplies in the logistics pipeline.

"A day without transportation is a problem, let alone a week," said another traffic manager for a large food products shipper who declined to be identified.

Even though the numbers of independent drivers is small, the traditional camaraderie between truckers gives rise to fears that most will obey calls to park their rigs, sending a message to Washington and the public.

"We're not concerned about our drivers or the companies we're contracting with us honoring this. But if this strike catches on, our freight could be held up at truck stops," said Dennis Lech, traffic services manager for Pfizer Inc., the New York chemical maker.

Several truck dispatchers for large commercial carriers have been warning that many drivers will either heed strike calls or refuse to run at night.

"I bet many call in sick or go deer hunting," one said.

This is not the first time that truckers have threatened to leave their tractors parked. The last effort to form a nationwide strike, in the late 1970s, sparked isolated violence in the east, but despite widespread delays, freight moved.

Last month's call for a job action, an Oct. 24 rally of 500 trucks outside CNN-TV's Atlanta headquarters, fizzled when only a few drivers showed.

The most successful truck strikes in recent memory were those organized by Canadian commercial drivers in September 1991 and Canadian owner-operators in May 1990 who blockaded several bridges connecting the United States and Canada, delaying freight for days.

The actions were taken over what Canadian truckers said was unfair competition from their American counterparts. Tempers flared several times during these protests, but the only violence reported were bruises and a few slashed air hoses.