In what Argentine authorities called a "major breakthrough" in the exhaustive investigation into the deadly 1992 bombing of the Israeli Embassy here, the Supreme Court issued an arrest warrant today for Imad Mughniyah, a leader of the militant Muslim group Hezbollah.

Authorities here believe Mughniyah, the second-ranking figure in Hezbollah's security service and one of the world's most wanted terrorists, ordered the attack that killed 22 people. In addition to that bombing, U.S. officials suspect him of plotting or participating in the 1983 bombing of the U.S. Embassy in Beirut and the 1995 hijacking of TWA flight 847 from Athens to Rome.

Today's arrest warrant was issued after authorities gathered what they called "conclusive evidence" that Hezbollah was behind the bombing. The evidence included handwriting identified as being from Hezbollah representatives on documents associated with the purchase of a truck used in the bombing.

Authorities also said they were able to establish that the truck was bought by a Brazilian who is believed to have ties with factions of Hezbollah operating in southern Paraguay, only a few miles from the Argentine border. It was from that poorly guarded border, authorities said, that terrorists involved in the bombing slipped into Argentina.

Iranian-backed Hezbollah has long been suspected in the bombing, and U.S. officials, who assisted in the Argentine investigation, have blamed Hezbollah publicly. Last year, Argentina expelled several Iranian diplomats based on information that they had conspired with Hezbollah in planning the attack. But today's arrest warrant is the first issued against the group by Argentina.

The move "proves that while there were mistakes and errors in the procedure of the investigation, the Argentine justice system still works," said Diego Guelar, Argentina's ambassador to the United States. "We have finally gotten to the person who was ultimately responsible for this horrible crime."

Despite the warrant, chances are slim that Mughniyah will ever stand trial. The United States and other law enforcement officials have been pursuing him internationally. Meanwhile, Argentina is continuing to investigate several local police officers believed to have aided in the embassy attack.