NEW YORK (AP) _ An admitted Mafia hitman, pleading guilty to obstruction of justice on Friday, said he falsely recanted his testimony about a mob leader in the ''Pizza Connection'' drug trial because of threats to his family.

Luigi Ronsisvalle said he knew a sworn affidavit retracting his previous testimony was a lie, but he signed it ''because my family was in danger.''

Ronsisvalle, who has admitted committing 13 contract murders, entered his guilty plea in a heavily guarded federal courtroom in Manhattan.

His lawyer, Henry Putzel III, said Ronsisvalle knowingly signed a false statement recanting his testimony against convicted Bonnano crime family leader Salvatore Catalano because of ''serious and extraordinarily real threats'' on the lives of his wife and children.

He entered the plea as part of an agreement to cooperate with prosecutors, Putzel told U.S. District Judge David Edelstein.

Ronsisvalle, 47, a native of Sicily, faces a maximum penalty of five years in prison and a $250,000 fine on the obstruction charge.

At a news conference afterward, U.S. Attorney Rudolph Giuliani said Ronsisvalle was threatened while in the federal Witness Protection Program and the Marshals Service is investigating.

There was ''no suggestion the breach of security was caused by a government employee,'' he said.

Ronsisvalle and his family were placed in protective custody early Tuesday after Ronsisvalle called authorities about the threats, he said.

Ronsisvalle told the judge he was contacted by phone about three weeks ago ''in my own language - Sicilian.''

He said the callers said they knew where his wife and daughters were and threatened to harm them if he did not change two points of his testimony against Catalano.

''And I said OK, because I know my kids, now they are under a shotgun,'' said Ronsisvalle.

He said he was instructed to contact Catalano's trial lawyer and change his story. After he signed an affidavit recanting his testimony, Ronsisvalle said, he expected to be killed.

''How come I'm still alive? I don't know. These guys don't know what they're doing, maybe,'' he told Edelstein.

The judge released Ronsisvalle to the custody of federal marshals under conditions that were not made public. No sentencing date was announced.

Outside the courtroom, Putzel said his client ''was distraught to the point of suicide'' and twice tried to takee that he had given it tapes of his conversations with Ronsisvalle at his recantation.

Another lawyer for Catalano, Mario Malerba, on Thursday withdrew the retrial motion filed by Fisher, saying it was premature, and charged that Fisher had not been authorized to make the motion.

Fisher denied it but withdrew from the case on Wednesday, saying he could not be both counsel and witness in the case.

Giuliani said he was seeking civil sanctions against the lawyers involved in Ronsisvalle's recanting.

''There are some very, very serious questions of unethical behavior,'' said Giuliani, who would not say if the lawyers knew of the threats against Ronsisvalle.

Ronsisvalle's testimony last year helped convict Catalano, a Queens bakery owner, of participating in a massive heroin importing operation dubbed the ''Pizza Connection'' because it allegedly used pizza parlors as fronts.

Catalano was sentenced to 45 years in prison and fined more than $1 million as a leader of the ring, which prosecutors said imported $1.6 billion in heroin in nearly a decade. He is serving his sentence at the federal penitentiary in Leavenworth, Kan.