Papal assailant Mehmet Ali Agca refused to appear in court today after providing contradictory testimony about his alleged Bulgarian and Turkish accomplices in a conspiracy to murder Pope John Paul II.

In a message to the court investigating the papal plot, the 27-year-old Turkish gunman said he was staying away from the trial today as he wanted to rethink his position. Agca has said that the assassination attempt on the Polish-born pontiff was commissioned by Soviet and Bulgarian officials.

Agca's refusal to be cross-examined by the court comes as his credibility has sunk to an all-time low following dozens of retractions, contradictions and obvious untruths in his testimony. At the last session, Tuesday, the prosecutor accused him of "leading the justice authorities around by the nose for two years."

In Agca's absence, Judge Severino Santiapichi began interrogation of the leader of a right-wing Turkish emigre organization in West Germany, Musa Serdar Celebi, one of five Turkish defendants in the case. Celebi, 33, has been accused of providing logistical support for Agca and other members of a rightist terrorist group known as the Gray Wolves.

A defense lawyer for the accused Bulgarians, Giuseppe Consolo, said Agca was "afraid" to be cross-examined further by the judge after making so many errors.

"He knows that his story hasn't convinced anybody -- and that's why he is refusing to appear," Consolo told journalists.

Prosecutor Antonio Marini said that the court could resume its cross-examination of Agca following the testimony of Celebi. He noted that the Turk has refused to answer questions on two previous occasions during the month-long trial, even though this is the first time he has declined to appear in court.

Agca's latest difficulties began on June 19, when, under heavy pressure from the judge, he admitted for the first time that two other Turks had been with him in St. Peter's Square in May 1981 when he shot the pope. He had insisted earlier that only one Turkish accomplice had taken part in the assassination attempt with support from three former Bulgarian officials in Rome.

After conceding the presence of the third Turk, Agca was obliged to change the entire structure of his story as the judge uncovered contradictions and inconsistencies in his account.

In a written message from his prison cell, Agca said, "The undersigned, Mehmet Ali Agca, is not appearing at the trial today for reasons of further rethinking."

When Celebi was summoned to the witness stand, he reserved the right to refuse to answer certain questions, arguing that his answers might later be used by Agca in thinking up a new story. "I want to reply to the court's questions, but I don't want to be Agca's victim a second time," he said.

In today's cross-examination of Celebi, Santiapichi attempted to demonstrate links between his emigre organization and extreme right-wing nationalist politicians in Turkey. Like the Bulgarian defendants, Celebi has denied having anything to do with the papal plot, but he has acknowledged meeting twice with Agca in the months before the shooting.