The U.S. evidence meant to persuade Italian authorities to arrest Mohammed Abbas in connection with last week's hijack of the Achille Lauro arrived 30 minutes after the Palestinean had been allowed to leave the country, according to Defense Ministry sources, and it was delivered by Israeli intelligence.

A communique from Defense Minister Giovanni Spadolini, quoted by the daily La Stampa today, gave credence to Prime Minister Bettino Craxi's arguments in a Cabinet meeting yesterday that Abbas was allowed to leave Italy because the United States had failed to produce the evidence to justify his arrest under Italian law before he left on a Yugoslav airliner last Saturday.

In a separate development, two Arabs with Moroccan passports were arrested here, police said, after arriving from Iraq carrying explosives that one described as meant for use against Americans and Israelis.

More curious than the timing of the arrival of the U.S. evidence, according to sources close to the defense minister, was that the tape was not delivered by the U.S. government as promised but by Mossad, the Israeli intelligence agency. The evidence was described as a tape recording of a conversation Abbas held with the four hijackers in the course of persuading them to surrender.

Furthermore, these sources stated, instead of the tape going to the governmental and judiciary officials concerned, it went to the Italian military intelligence organization and was not delivered to Craxi until late Monday night -- long after a major dispute had broken out between Craxi and his defense minister over the handling of the Abbas affair.

A Defense Ministry spokesman confirmed the existence of the tape and the gist of its peregrination through the Italian bureaucracy but refused to comment on its content, which was termed secret.

A source that has heard it said, however, that it was "not sensational" and could not prove or disprove U.S. allegations that Abbas actually directed the hijacking.

The tape, according to Italian official sources, has Abbas identifying himself to the hijackers as "Abu Khaled," his nom de guerre and being greeted by them, apparently members of his Palestine Liberation Front, who respond that they are "awaiting his orders." Abbas had been asked to intervene by his superior in the umbrella Palestine Liberation Organization, Yasser Arafat, after Craxi sought Arafat's assistance.

Abbas' orders, according to the source, were that the hijackers surrender immediately, leave their arms behind, prepare to abandon ship and admit that their mission was not the hijacking of the ship but a terrorist raid on the Israeli port of Ashdod, one of the Achille Lauro's scheduled ports of call.

"From our point of view the tape is not proof that Abbas was involved in the highjacking," said the official source who heard the tape. "It can be taken either way."

Craxi has credited Abbas with having successfully negotiated the four hijackers' surrender and thus saved others from the fate of Leon Klinghoffer, the slain American passenger.

Abbas was brought to Italy with a close aide and the four hijackers early last Friday when U.S. Navy F14 jets intercepted the Egyptair Boeing 737 that was flying them from Cairo to Tunis, seat of Arafat's PLO, where the four hijackers allegedly were to be tried by the organization.

U.S. officials acceded to the Italian insistence on tryng the hijackers in Italy, then turned their attention to Abbas, whom they proclaimed a major terrorist. A federal judge issued a warrant for his arrest and extradition proceedings were begun to try to prevent his leaving Italy.

According to sources close to the prime minister, the moves against Abbas began here at 3:30 a.m. Saturday morning, when Justice Minister Edwin Meese III telephoned his Italian counterpart, Interior Minister Oscar Scalfaro and asked the arrest of Abbas, promising that documents to establish guilt were on the way.

Some hours later, by this account, the FBI sent a written document expressing the same intentions to the Italian Interpol, which immediately passed the document to investigating magistrates in Genoa, from which the Achille Lauro had sailed, in Syracuse, where the four hijackers were being held, and in Rome.

Defense Minister Spadolini declared today that the promised evidence did not arrive until 7:30 p.m. Saturday night -- 30 minutes after Abbas and the other PLO aide had been allowed to board the Yugoslav airliner for Belgrade.

The officials did not address directly the question of why Italy chose not to wait for the promised evidence before letting Abbas go. But it appeared that the intention from the outset was to free him, for the reasons given subsequently.

The fallout of the affair continued, today, with Craxi's 26-month-old coalition government still threatened.

The heart of the dispute lay in a bitter dispute between Craxi and Spadolini over Abbas having been allowed to leave the country without the defense minister, a key member of the government's five-party coalition, being consulted.

Late tonight, however, the crisis seemed to have eased somewhat when Craxi and Spadolini agreed to meet on the issue.

One of the two Arabs seized today said a 20-pound bomb found in his suitcase at Rome airport was intended for use against Americans and Israelis, said police. The second man was held at the central train station as he got off a bus from the airport. A similar bomb was found in his locker, they reported.

Both arrived on a flight from the Iraqi capital and were traveling on Moroccan passports, from Baghdad, airport officials said, addding that the man arrested at the airport claimed he had nothing to do with the Achille Lauro hijacking and was a Moroccan who considered himself at war with Israel and the United States.