A delegation of high-level Polish bishops arrived here today to talk with Pope John Paul II in the latest of a series of discreet international contacts involving the Polish authorities, the Vatican, the White House and the Kremlin on the possible lifting of martial law.

Speaking to reporters at Rome's airport on his arrival from Warsaw, Cardinal Jozef Glemp, the Roman Catholic primate of Poland, denied suggestions that the church planned to set up a "neo-Solidarity" union under its own auspices. He depicted the political situation in Poland as fluid following John Paul's visit, amid concern about church negotiations with the Communist authorities on setting up a fund to assist Polish farmers.

The timing of the Polish bishops' visit underlined the active personal role being played by John Paul in seeking to resolve the political and social deadlock in his homeland. Scarcely a week after returning to the Vatican from a grueling eight days on the road, he is again taking time out from the demands of the universal church to concentrate on Poland.

The pace of international diplomatic activity over Poland has quickened noticeably since the papal pilgrimage. Both Vatican and Polish officials acknowledge the importance of "outside factors," including the amount of leeway given to the Polish leadership by Moscow and the conditions set by President Reagan for lifting sanctions imposed after Gen. Wojciech Jaruzelski's military takeover in December 1981.

The talks between the pope and the Polish bishops followed several upbeat comments by senior officials in Warsaw about the papal visit. Jaruzelski was quoted in a Polish newspaper yesterday as saying that he and the pope had found "a platform of understanding" during their two meetings.

The exact nature of this "understanding" is difficult to establish since both the Vatican and the Polish authorities are saying little. The best guess among observers here is that, rather than being a clear-cut political deal, it is simply a joint striving to create conditions for lifting martial law and ending Poland's present international isolation.

Asked today whether it was possible that martial law might be lifted on July 22, Poland's national day, Glemp said: "One thinks so, one thinks so. I believe the church would want it but these are political questions which I have no part in."

The Vatican today took the unusual step of formally denying reports of a linked package agreement between the church and the Communist authorities in Poland covering the proposed agricultural fund, the establishment of a "neo-Solidarity" union under church auspices, and persuading Lech Walesa, the leader of the banned Solidarity trade union, to take a back seat. Vatican spokesman Romeo Panciroli said the issues were not related.

When questioned about reports of a church-sponsored union, Glemp replied: "I have never heard of anything like that." Another member of the delegation, Archbishop Henryk Gulbinowicz of Wroclaw, said it was "not the right moment to talk about the new union because the other one is not finished."

Glemp said he had not read a controversial article in the semiofficial Vatican newspaper L'Osservatore Romano suggesting that Walesa had agreed to step aside for the "greater good." The author of the article, the Rev. Virgilio Levi, was forced to resign as deputy editor, reportedly as a means of distancing the church hierarchy from his views.

The diplomatic challenge facing the pope and Jaruzelski is that they must somehow convince the Kremlin that its interests are being protected in Poland while simultaneously persuading the U.S. administration to lift the sanctions. The government also has to convince an extremely skeptical populace that it is sincere when it talks about "national reconciliation."

Reagan received a briefing on the initial results of the papal visit from Cardinal John Krol of Philadelphia who accompanied the pope to Poland. Soviet leaders presumably were told of developments during the Warsaw Pact summit meeting in Moscow earlier this week, which Jaruzelski attended.

A tentative sign of Soviet approval for the way the Polish leadership handled the papal visit was provided by Vadim Zagladin, the deputy head of the Soviet Communist Party's international department, during a trip to Paris this week. Talking to journalists following a meeting with French Foreign Minister Claude Cheysson, he described the situation in Poland as "developing well."

He said, "In the West, some thought that socialist Poland would explode after the pope's visit. Well, it hasn't exploded."

With Jaruzelski apparently ready to lift martial law and consider a limited amnesty for political prisoners, the key sticking point now seems to be the future of trade unions. In Poland, the pope repeatedly called for workers to be allowed authentic and independent unions but the Polish authorities have shown no sign that they are prepared to give way.

In his news conference yesterday Reagan made clear that the decision on whether or not to lift sanctions depends in large part on whether the Polish authorities allow "free unions not subject to government control."