As tensions between the Roman Catholic Church and the Polish authorities increase, sources in the Vatican are beginning privately to express doubts that Pope John Paul II's long-awaited visit to Poland in June will take place.
Vatican intelligence indicates that Poland's leader, Gen. Wojciech Jaruzelski , is involved in an enormous power struggle, which he may not win.
''Jaruzelski seems to be hanging by a string,'' said a high-ranking Vatican official who did not want to be identified. If there is a change in leadership, the Pope would not go to Poland, the churchman said.
Another official, Franz Cardinal Konig, this week told journalists in Vienna after a trip to the Vatican, ''It's not certain yet that the Pope will go to Poland. We cannot rule out that added problems will make the trip impossible.''
The Vatican sources said the trip was going forward and an advance team had left May 12 to prepare security arrangements. But they emphasized repeatedly that the Vatican never officially responded to the invitation, issued jointly by the Polish government and the Polish episcopate. The Pope accepted the invitation in a personal letter to President Henryk Jablonski.
Until now, the papal visit was expected to give Jaruzelski's regime a much-needed boost, for it would both legitimize his regime among Poles and demonstrate his independence from Moscow.
But a number of incidents directed against the Polish Catholic Church in the past week indicate that Jaruzelski's rivals in Warsaw, seemingly backed by the Kremlin, are gaining strength. The church is growing bolder in its responses to the attacks, giving some hints that churchmen think the situation may be beyond salvaging.
According to Vatican intelligence, the Soviet commander in chief of the Warsaw Pact forces spent two weeks in Poland in mid-April reforming the Polish Army. Many officers whose loyalty was in doubt were replaced by more politically reliable men.
The sources said that Jaruzelski, for the first time since Nov. 24, 1981 (the eve of the imposition of martial law), has dispatched senior military operations units to the countryside. The sources see this move as a sign that Jaruzelski feels his position is threatened and is trying to secure the country's nerve centers.
In the past week, several incidents have disturbed the church in Poland, demonstrating that the Pope's scheduled visit is being sabotaged from powerful quarters. According to a broadcast on Radio Warsaw, a priest was arrested May 11 for raising money for families of political prisoners. There was also a broadcast attack on the Pope for his failure to speak out in favor of Soviet leader Yuri Andropov's latest disarmament proposals.
Before May Day, Kazimierz Barcikowski, the senior government representative on the joint church-state committee, wrote to Poland's primate, Jozef Cardinal Glemp, asking that no masses be held on Sunday, May 1, when underground Solidarity leaders had called for mass protests. Glemp refused, and members of the regime have charged that the demonstrations and civil disturbances that occurred in some 20 cities and towns on May 1 originated at the Catholic masses.
In a strongly worded letter, church officials denounced an attack by six unidentified men who broke into the Franciscan convent in Warsaw last week and beat up four Catholic lay workers. Vatican circles see the incident as a direct attack on Glemp because the convent of St. Martin's ran a charitable dispensary under his auspices.
Sources note with anxiety that both the attack at St. Martin's and the arrest of the priest at this sensitive time could not have been carried out without the approval of Gen. Czeslaw Kiszczak, interior minister and chief of police.
The Vatican has reacted to the stepped-up pressure, but it has been careful not to jeopardize the Pope's trip. A banner headline in the Vatican's newspaper, L'Osservatore Romano, read, ''Don't abandon Poland.'' The page was devoted to the 19th-century Italian General Garibaldi's appeal a hundred years ago to Europe to save Poland.
In the same issue, the paper front-paged a news story about the arrest and sentencing of two priests who founded the Catholic committee for the defense of the rights of believers in Lithuania.
The Pope has been very involved in planning his trip. According to the Rev. Albert Krapiec, rector of Catholic University in Lublin, the Pontiff recently sent him a letter asking him to ''make every effort to persuade the authorities to make my visit to Lublin possible.'' At present Lublin is not on the agenda for the Pope's trip to Poland.