A Soviet Aeroflot jetliner remained parked at New York's Kennedy Airport last night as wrangling over the future of one passenger -- ballerina Ludmilla Vlasova -- threatened to escalate into a major diplomatic incident between the United States and the Soviet Union.

At issue in the dispute, which began late Friday, was whether Vlasova was returning to the Soviet Union of her own free will or whether she was being coached by Soviet officials after he defection of her Bolshoi Ballet star husband, Alexander Godunov.

Soviet officials, charging that U.S. refusal to allow the plane's departure was "an unprecedented provocation," continued to refuse permission for Viasova to be interviewed by American officials outside the airliner.

On the other side, U.S. officials, contending they were acting under the mandate of U.S. and international law, said they would not back down from their insistence on talking with Vlasova in an environment where they could be certain she was not speaking in fear or under duress.

The seriousness with which the matter was being viewed was underscored by the fact that Warren M. Christopher, acting secretary of state, was directing U.S. negotiations with the Soviets personally from Washington, U.S. efforts in New York were being headed by Donald F. McHenry, deputy head of the U.S. mission at the United Nations.

While the behind-the-scenes negotiating was going on, the Soviets were issuing angry statements and charges that American officials had forced their way onto the plane, taken Vlasova's passport from her "by deceit" and, at the time they boarded the plane Friday, "already had a U.S. passport prepared in her name without her knowledge."

These charges were denied by the State Department as "totally false and without any basis whatsoever." Department officials said U.S. immigration officials had entered the plane "in a normal fashion." Officials confirmed they had taken Vlasova's passport temporarily "for purposes of identification" but said it was returned to Soviet officials Friday evening.

The confrontation began building up Thursday when it was announced that Godunov, in the United States on a Bolshoi tour, had requested and received asylum in this country. In defecting from the ballet company, he left behind his wife, who also is a Bolshoi soloist.

Godunoy, who had gone to an undisclosed location, made it known through his attorney, Orville Schnell, that he wanted to speak with his wife.

Mary Ann Bader Debeusscher, a State Department press aide, last night gave this account of what happened next:

Late Friday afternoon, the department learned that Vlasova was aboard the Aeroflot plane, scheduled to leave New York for Moscow at 5 p.m. She had been put on the plane although the rest of the Bolshoi company is remaining here to complete its U.S. tour.

Debeusscher said Vlasova's projected departure violated an order issued by the Immigration and Naturalization Service after consultation between the State and Justice departments. The order said Vlasova could not leave until she had been interviewed "in noncoercive surroundings to determine whether she was leaving of her own free will."

Debeusscher added that the Soviet embassy here had been informed by State both Thursday and Friday that Vlasova could not leave without such an interview, and said embassy officials had indicated their understanding that the United States had the right to conduct the interview.

The "prevention of departure order," which led to the aircraft being physically prevented from leaving, was issued under the provisions of the immigration and Nationally Act. Section 215 of the act prohibits transporting a person out of the country who has been ordered legally to remain.

The State Department's account said, "The circumstances under which she boarded the plane certainly raise questions about the voluntariness of her departure." It added:

"We have clear obligations, on the basis both of U.S. and international law, as well as on humanitarian grounds, to ensure that no one is repatriated to any country against his or her will. Further, anyone on U.S. soil enjoys the protection of U.S. law. We hope for a speedy, lawful, and humane solution"

However, the bellicose tone of Soviet public statements about the incident indicated that Moscow did not intend to back down and allow Vlasova to be taken off the plane, which legally is outside U.S. jurisdiction. A statement issued yesterday by the Soviet embassy here said:

"We do reject what is happening as a very serious matter and qualify it as a very serious provocation against a Soviet citizen and against the Soviet airline, which amounts to a provocation against the Soviet people and the Soviet Union."

An embassy spokesman said official Soviet protests had been made to the State Department and to the U.S. embassy in Moscow.

State Department officials countered that a U.S. protest would be made to the Soviets. But, when asked about the nature of negotiations and the chances of breaking the stalemate, the officials replied: "We are unable to characterize matters relating to private diplomatic communications between the U.S. and Soviet governments."

In New York, meanwhile, Soviet officials at the airport continued to insist to reporters that Vlasova wanted to go home and was refusing of her own volition to leave the plane. Aboard the jetliner with her were about 70 homeward-bound Soviet citizens. Forty Americans who were aboard the plane were taken off early yesterday after waiting for more than 10 hours.

McHenry, briefing reporters at the airport last night, said that the United States had offered Friday night to let Soviet citizens off the plane, but that Soviet officials refused to allow this.

Yvgeny N. Makeyev, deputy Soviet chief delegate to the United Nations, appeared later last night at the gate where the plane is being detained.

"They [U.S. officials] want her to leave the place, but she doesn't want to leave the plane," he said. "She doesn't like the way she has been treated by the representatives of the United States.

"This is her decision to stay on the plane. No one is exerting pressure on her."

Soviet officials had offered to let a pool of American reporters board the plane and interview Vlasova, but U.S. officials refused the offer for tactical reasons.

"The point is to get her off the plane -- not to get another person on the plane," said a State Department officials. He said that in all likelihood the dancer would appear calm enough for a reporter to conclude that she is not being held against her will.

Officials at the Justice Department said the U.S. Soviet confrontation over the departure of a Soviet citizen was not unprecedented.

The officials said they believed the last such incident occurred in January 1972, when a 36-year-old Soviet student, Merab Kurashvili, who had been involved in a shoplifting incident, was ordered home by Soviet officials and tried to slash his wrists at Kennedy Airport.