Persistent efforts by a magistrate to charge PLO leader Yasser Arafat with supplying arms to Italian terrorists have run up against bureaucratic obstacles and are being pointedly ignored by the Italian government.

Despite warrants issued by Venice Examining Magistrate Carlo Mastelloni, 34, charging that the Red Brigades received weapons from the Palestinan Liberation Organization, Italian Prime Minister Bettino Craxi and Foreign Minister Giulio Andreotti met for more than two hours with Arafat during an official visit to Tunisia last month.

Mastelloni issued an arrest warrant in September for Arafat and one of his top aides, Salah Khalaf, also known as Abu Iyad and identified as the security chief of Fatah, the principal PLO faction. The charges, introducing weapons into Italy and holding them for terrorist purposes, have been labeled "absurd" and "ridiculous" by PLO representatives in Rome.

Italy does not recognize the PLO officially, but the organization has an office in Rome, and several key political groups here have good relations with Arafat. The PLO leader visited Italy in September 1982, when a Venice prosecutor had already made the first charges, and again last June for the funeral of Communist Party leader Enrico Berlinguer.

Judicial sources in Venice and Rome say they believe that since the 1973 attack by Palestinian terrorists on a Pan American plane at the Rome airport there has been a tacit understanding between Italy and the PLO to allow the Palestinian organization to have a political office here in exchange for a ban on terrorist actions on Italian territory.

The meeting in Tunisia, primarily to discuss a renewed Middle Eastern peace effort backed by the European Community, of which Italy assumes the presidency next month, has caused anger among the more moderate parties in Italy's five-party coalition and led Israeli Prime Minister Shimon Peres to postpone a scheduled visit here.

Judicial sources in Venice said that as chief of the Italian executive branch, Craxi is free to make any kind of diplomatic arrangements he wishes. "But the meeting with Arafat certainly appears to be a slap in the face of the Italian judiciary," said an irate Venice magistrate.

Government representatives have denied that the meeting with Arafat was meant in any way to offend the judiciary. "It is simply that the search for peace in the Middle East is more important than a judicial tangle," said Antonio Ghirelli, chief spokesman for Craxi. "The search for peace is more important than the prestige of a magistrate."

Ghirelli, who would not comment on the merits of the case, pointed out that the decision to meet with Arafat also reflected the facts that no request has been made for Arafat's extradition and that there has not yet been a trial. "In Italy, until there's been a trial and a sentence every defendant is innocent before the law," he said.

Government sources have denied that any pressures have been exerted by the executive branch on Mastelloni or any of his colleagues and say the slow progress of the case reflects typical Italian judicial cavils.

The arrest warrant for the PLO representatives was the second issued in the past 15 months by Mastelloni, who earlier this year concluded a major investigation into the activities of the Red Brigades' Venice "column," the same group that in December 1981 kidnaped U.S. Army Brig. Gen. James L. Dozier.

The first warrant, issued in September 1983 and basically identical to that now on the books, was revoked a year ago by a higher ranking judge. Mastelloni filed an in-house appeal with the Council of the High Magistrature, the governing body of the independent Italian judiciary, which last spring ruled that the case be returned to him, enabling him to make a fresh start.

The latest warrant contends that Arafat "approved a joint program of collaboration" with the Red Brigades and "authorized, for subversive aims, the supply of a huge quantity of arms and munitions that was brought by sea into Italy in September 1979." It has been challenged by defense lawyers.

But on Oct. 8 it was upheld by a three-judge tribunal, which ruled that the existing evidence, provided largely by close to a dozen "repentant" terrorists, while not complete, was sufficient to justify arrest warrants in the case of both the defendants.

The tribunal's unpublished ruling, obtained by this reporter, said "the presumptive significance of the facts listed is certain and unequivocal with regard to the hypothesis of responsibility of both the defendants." Nevertheless, the existence of the warrants as well as the substance of the charges, appears to be discounted by top Italian government leaders.

Mastelloni, who in 1982 had turned down a prosecutor's first request for a warrant against Arafat, now reportedly is thoroughly convinced by the evidence that in the late 1970s Arafat involved his Fatah faction of the PLO in a "pact of collaboration" with Italy's Red Brigades.

According to the arrest warrant, which also was obtained, Mastelloni has relied on testimony by at least 10 former Italian terrorists who either participated in a sailing expedition to get the weapons, or had been given information by a top Italian terrorist about the arms shipment or about a series of meetings in Paris between the Red Brigades' representatives and Khalaf.

Mastelloni is known to consider as key evidence -- which changed his originally negative assessment in 1982 -- a four-page memorandum written by Giovanni Senzani, then the top Red Brigades leader, and found in his Rome apartment when he was arrested in January 1982. The memo was passed on to Venice authorities the following year.

According to the arrest warrant, the memorandum, written in a sort of shorthand code, and later "translated" by one of Senzani's closest aides, is the summary of a meeting of European terrorists in Paris at the end of 1981 and refers specifically to a Red Brigades-PLO agreement.

"The . . . note, thus, helps to demonstrate, confirming it, the clandestine nature of a lasting and multiannual agreement, organized in a joint plan of collaboration between the Red Brigades . . . and the highest levels of Fatah, the majority faction of the PLO -- of which Arafat has always been the unchallenged leader," reads the arrest warrant.

The specific charges against both Arafat and Khalaf, however, focus primarily on a large arms cache that five Italian Red Brigades terrorists brought to Italy from Lebanon in September 1979 on a sailing ship named the Papago.

Following an agreement reached in Paris by Khalaf and Mario Moretti, who preceded Senzani as leader of the Red Brigades, Moretti sailed to Lebanon with terrorists Riccardo Dura, Andrea Varisco, Sandro Galletta and Massimo Gidoni in August 1979.

Judicial sources say testimony provided by Galletta, who after turning state's evidence recently was released from prison, indicates that after a brief stopover in Cyprus, the Papago docked in southern Lebanon, somewhere in the vicinity of Sidon. It allegedly took on a shipment of arms consisting of 150 L2A3 Sterling submachine guns, five bazookas, 10 surface-to-air missiles, antitank and antipersonnel bombs, several dozen Belgian FAL rifles several pounds of plastic explosive and "thousands" of bullets.

In September 1979, the arrest warrant says, the Papago returned to Italy, landing on the Adriatic coast near Quarto d'Altino near Venice. The weapons were taken first to a garage in Mestre, where most of them were divided among representatives of the Red Brigades' five Italian columns and taken away by train in valises, the sources said.

Several former terrorists, including Antonio Savasta, a member of the Red Brigades' executive council who masterminded the Dozier kidnaping and was arrested during the general's rescue, have said that the remaining weapons -- judicial sources speak of one-sixth of the original shipment -- were to be kept in Italy for use by the PLO and were taken to nearby Volpago del Montello where they were buried.

Revelations arising from the capture of Dozier's kidnapers led to the investigation of a PLO-Red Brigades connection.

In February 1982 Savasta led police to this arms cache, where rifles were found wrapped in pages from an Arab-language Middle Eastern newspaper.

The Sterling submachine guns found in this cache have been traced to a shipment of 3,500 sold by the English factory to Tunisia between 1958 and 1960. The arrest warrant also refers to information provided to a parliamentary investigating commission by a former military intelligence officer who had said 11 more Sterlings seized by Italian police at various times and, like those found at Montello, all with serial numbers beginning KR, appeared to be from part of the original shipment that the Tunisians had given to the PLO representative for Arafat in 1968.

Because it refuses to recognize Italian jurisdiction in the case, the PLO itself has not become directly involved. But Giobatta Gianquinto, a lawyer and Communist former mayor of Venice who was appointed by the court to defend Arafat and Khalaf, insists Mastelloni's case has no legal foundation.

According to Gianquinto, two procedural questions preclude continuation of the case against Arafat. An appeal filed with Italy's highest court claims that as the head of the PLO, which enjoys recognized international status, Arafat, under Italian law, should enjoy the same penal immunity as a head of state.

"The fact that Craxi just met with Arafat in Tunisia is further proof of Arafat's status," said the lawyer. His appeal also maintains that because the case involves a foreign citizen who allegedly committed a crime on foreign territory, the warrant against Arafat ought to have required authorization by the Italian minister of justice.

The defense lawyer also says the testimony provided by the former terrorists regarding the meetings in Paris involve no firsthand accounts, and that Savasta became a Red Brigades executive committee member only in 1981 and is unlikely to have been told things earlier about the group's international ties in such detail by Moretti.