The Turkish gunman who shot Pope John Paul II has introduced the key issue of possible international ties to the alleged conspiracy, testifying today in court that he had been trained as a terrorist by Bulgarian and Czechoslovak experts in Syria.

Mehmet Ali Agca, who is serving a life sentence for the attempted assassination of the Polish-born pontiff in May 1981, added: "I can say with certainty that the political and financial center of world terrorism is the Soviet Union."

Three Bulgarians and four Turks went on trial here last week as Agca's alleged accomplices in the conspiracy.

Replying to questions from Judge Severino Santiapichi, Agca at times contradicted earlier pre-trial testimony and appeared reluctant to go into details about his terrorist activities in Turkey. In off-the-cuff remarks to photographers crowding around his metal cage at the beginning of the session, he repeated claims originally made last week that he was "Jesus Christ" and that the world would end shortly.

Asked to describe how he had begun his terrorist career, Agca said he had accepted money and support from a right-wing Turkish group known as the Gray Wolves while at the university in Ankara. He added that he had spent part of 1977 at Latakia in Syria with other Gray Wolves being trained as a terrorist by "Bulgarian and Czech experts."

"In this camp there were also western terrorists, French, Italians, Germans, and Spanish. The camp was under the control of the Syrian secret service," Agca said, pronouncing his words deliberately in halting but concise Italian.

When first arrested after shooting the pope in St. Peter's Square, Agca told Italian magistrates that he had been trained as a terrorist in Lebanon in 1977. His subsequent claims to have received guerrilla training "in Palestine" were rejected in an official report by a Turkish military judge last year, in connection with Agca's conviction as the murderer of liberal Turkish editor Abdi Ipekci, on the grounds that they were "not serious."

Antonio Albano, the Italian public prosecutor who drew up indictments of Agca's alleged accomplices last year, stated as a fact in his report that the pope's would-be assailant had been trained in Syria. So far, however, no evidence has been produced by Italian magistrates to support this claim.

Agca also appeared to contradict earlier testimony when asked to explain the meaning of a letter to a Turkish newspaper which he wrote shortly after escaping from a top-security military prison in November 1979 after the Ipekci conviction. In the letter, which was couched in extreme nationalist jargon, he threatened to shoot the pope, who was on a visit to Turkey.

In one version of his pre-trial testimony, Agca said the point of the letter had been to create a diversion to allow him to escape from Istanbul while the police concentrated their attention on protecting John Paul. Today, however, he said he really had intended to kill the pope but changed his mind because of "tight security."

Agca said the letter had been approved by Oral Celik, a prominent member of the Gray Wolves who helped arrange his escape from jail and acted as his mentor. Celik, who has been accused by Italian magistrates of being a second gunman in St. Peter's Square in May 1981, is on trial here in absentia.

In an apparent attempt to catch Agca off guard, the judge jumped back and forth in his interrogation between events in Turkey and in Italy prior to the papal shooting. At one point, he asked Agca about a memorandum in Turkish found in his Rome hotel room after his arrest that included a phrase about a possible trip to "Florence or Naples" so as "not to attract attention around the Vatican."

Insisting that he had written the memo himself as part of his planning to shoot the pope, Agca said: "I had to keep away from the Vatican so as not to attract the attention of the police. I was wanted in 45 countries" for the Ipekci killing and the escape from prison.

In pre-trial testimony, Agca said he had been to St. Peter's Square for three successive days before the assassination attempt on May 13 for dress rehearsals with his alleged Bulgarian accomplices. He told Italian magistrates that he met the Bulgarians in well-known public restaurants and bars in Rome.

The pope's would-be assassin said that members of his group had raised funds for terrorism through smuggling and contraband. He said that Celik had close contacts with a notorious Turkish smuggler, Abuzer Ugurlu, who he described as linked to the Bulgarian authorities.

Asked to be more precise about the source of his funds, he replied: "You have to understand, I was not interested in money. For me money was a simple instrument that made it possible to achieve certain objectives. Lenin also said this."