Eastern Airlines Inc. eliminated service to Salt Lake City and 56 other domestic and foreign cities Friday and curtailed flights to 50 other cities as 8,500 ground workers struck the financially troubled airline early Saturday.

It was the climax to 17 months of bitter negotiations, in which union leaders accused the carrier of trying to provoke a walkout. Eastern's pilots were urged by their union to honor the picket lines."Its 12 o'clock, put the pickets on," said Marty Urra, president of Local 702 of the International Association of Machinists. "It's a shame. It could have been avoided."

The strike began moments after midnight, hours after President Bush refused to intervene in the dispute. At negotiations in Washington about 90 minutes before the strike began, Eastern made an offer to the International Association of Machinists, but it was not enough to avert a strike.

After meeting with the secretaries of labor and transportation Friday, Bush decided against the recommendation of the National Mediation Board, which had called for the appointment of an emergency board.

Bush could have delayed the strike deadline by 60 days by appointing the three-member panel to review the dispute. But he said he had no reason to believe the delay would produce an agreement.

The president also urged union leaders not to seek to disrupt the nation's transportation system through secondary boycotts - employees of other airlines or of railroads honoring Eastern picket lines - and he said the Department of Transportation would monitor the situation.

Bush said if secondary boycotts threaten to disrupt essential transportation services, he would seek legislation to prohibit the use of the tactic against neutral companies. The machinists' union has vowed to use secondary boycotts.

Henry Duffy, president of the Air Line Pilots Association, said the union recommended its Eastern pilots honor IAM picket lines. He also said ALPA recommended its members working for other airlines follow procedures to ensure safe flight operations in light of the Eastern strike and said the actions may cause delays on other airlines by Tuesday.

Transportation Secretary Samuel Skinner warned unions the government would not tolerate "threats of sabotage" or "economic blackmail" through secondary boycotts, and the Federal Aviation Administration would ensure all Eastern planes are safe.

"I just want to emphasize again that we will work tirelessly to ensure that if a strike occurs, Eastern's service will be on planes that are safe and airworthy, and that we will not tolerate any threats of sabotage or other forms of physical harm that threaten the health and safety of people on the ground or in the air," Skinner said.

A proposal made by Eastern Thursday to reduce economic concessions it was seeking from the IAM and greeted with enthusiasm by the National Mediation Board was spurned by union negotiators. Friday night's offer by the airline also was not accepted.

Eastern sent its machinists and baggage handlers home Friday, citing fears of sabotage. An Eastern executive said sabotage had become more common since February, and company officials said they had learned machinists were planning to disable the airline's fleet by deploying emergency evacuation chutes on planes as they walked off the job.

Wally Haber, general chairman of IAM's District 100 in Miami, disputed the allegation. "Let me tell you something, that is outrageous. Our people respect the aircraft they work on. They are professionals. They do not do childish, stupid things like that," he said.

Management workers took over maintenance of Eastern's planes after the IAM members were sent home with pay at 10:30 a.m. Friday. Replacement workers also were ready.

Leaders of the IAM have sought to characterize the strike as a crusade against Frank Lorenzo, chairman of Texas Air Corp., who bought Eastern in a last-minute deal brokered in February 1986.

Lorenzo is widely regarded by labor leaders as a union buster. The leadershipof the IAM has maintained that Eastern has been seeking to force a strike from the onset of the talks that began in October 1987.

The company has denied the allegation, and said making Lorenzo the target of a strike ignores the real economic issues separating company and management.

Leonard said the company had no replacement pilots lined up. He said he believes he can keep 800 pilots working, 25 percent of Eastern's force of 3,200.

Eastern, which is seeking pay cuts to staunch its $1 million-a-day losses, softened its demand for wage concessions from IAM mechanics and baggage handlers Thursday, the same day Eastern pilots announced that they had rejected a company bid for their support in the event of a machinists strike.

Transportation officials were concerned about the ripple effects of that strike, particularly if the IAM engaged in secondary picketing of other airlines andrailroads, which is allowed under the Railway Labor Act.