Relations between Czechoslovakia and the Vatican, which began to thaw last year, stirring hopes of relief for one of Eastern Europe's most restricted Roman Catholic communities, remain frozen over basic issues.

An exchange of visits in 1984 allowed senior Czechoslovak and Vatican officials to test each other's readiness for compromise after a three-year break in contacts. But government and church authorities in Prague say no date to resume talks has been set following the last meeting seven months ago. Neither side seems to have any idea when serious negotiations might begin.

What happens on the religious front here is important to Vatican policy for Eastern Europe since Czechoslovakia has the second-largest concentration of Roman Catholics in the region after Poland. About 60 percent of the country's 15 million citizens are at least nominally Catholic, according to church figures.

Improving relations with the Vatican have, in turn, apparently become a higher priority for the Prague government in view of a modest religious revival reflected in growing church attendance, the spread of underground religious publications, an expansion of unofficial discussion groups and of masses held in private homes and a rise in the number of theology students.

Concerns about the strength of this increase in religious activity -- and about the designs generally of Polish-born Pope John Paul II toward the Soviet Bloc -- are thought to have made the Czechoslovak government eager to reopen channels to the Vatican, closed in 1980 following the labor upheaval in neighboring Poland. But no one was surprised to see the church-state talks quickly stall again.

"Neither side, I think, has been willing to give much up, and now they realize it," observed a western diplomat.

"There are many difficulties," acknowledged Vladimir Janku, head of the government's Office for Religious Affairs, who in an interview last week sought to dispel the notion that no movement had taken place. He said his visit to Rome last July and a visit to Czechoslovakia in March by the pope's trouble-shooter for Eastern Europe, Archbishop Luigi Poggi, were never intended to produce "spectacular results."

"We've been exchanging views on how to set up conditions for talks," Janku said. "The negotiations haven't started yet."

He characterized his talks in Rome with Cardinal Agostino Casaroli, the Vatican secretary of state, as "very friendly and very hopeful," and said agreement on general principles had been reached affecting two main points of dispute -- the existence of the state-sponsored clerical group Pacem in Terris and the appointment of new bishops to vacant dioceses.

But in a separate interview, Cardinal Frantisek Tomasek, head of the Czechoslovak church, indicated that both sides were still far apart.

At the core of the deadlock is what to do about Pacem in Terris, which the government would like the Vatican to recognize, but which is regarded as a target of a 1982 Vatican decree forbidding priests to join political organizations.

Janku insisted that the group is a "nonpolitical organization, a free association of clergymen, working for peace and church-state cooperation." He said he was assured personally by Casaroli that the 1982 decree did not necessarily apply to the Czechoslovak case and was told that two criteria -- whether an organization split the church and whether it brought the church into conflict with the government -- determined if a group fell under the ban.

"We came to agreement that neither is the case with Pacem," said Janku.

The decree itself does not cite any specific groups, but Tomasek recalled that Cardinal Silvio Oddi, who headed the Vatican council that drafted the ban, said at the time it applied to Pacem in Terris.

"The state should respect the directives of the church," Tomasek declared. "It should respect the competence of the church in questions which are internal to the church."

Yet the government shows no signs of backing down. Janku said that Vatican recognition of Pacem in Terris "would benefit the development of the church in Czechoslovakia and relations with the Vatican." As if to underscore the state's commitment to its clerical creation, the Communist-controlled press gave prominent coverage earlier this month to a Pacem in Terris congress, including a photograph of party chief Gustav Husak shaking hands with Bishop Josef Feranec of Banska Bystrica, who was at the conference.

Just how large the movement is remains a point of dispute. Janku said one-third of all clergymen belong, but Tomasek estimated that at most 10 percent of all priests are members. He said many quit after the Vatican ban. The cardinal said two bishops -- Feranec and Josef Vrana of Olomouc -- participate without his approval in the belief that their involvement might facilitate the solution of church-state problems.

Tomasek, 85, has in recent months taken a more outspoken stance toward the government in an attempt to advance church rights. He has developed contacts with dissident clergymen and unnerved authorities by inviting the pope to visit Czechoslovakia in July on the 1,100th anniversary of the death of St. Methodius, the first archbishop of what now is Czechoslovakia. When John Paul accepted, the minister of culture informed Tomasek that conditions for a papal visit were not right at this time.

"We should have no illusions," said the cardinal in his large, high-ceilinged office overlooking the cobbled square in front of Prague Castle. "We know the Communist Party has as its program the aim of liquidating all churches and denominations step by step. When state bodies speak about protecting freedoms guaranteed the church, they have in mind liturgical activities in church buildings. They won't allow the church to get into public life.

Pulling out a typewritten page of statistics, Tomasek said something must be done about the severe shortage of priests and nuns resulting from state restrictions on admission to the country's two Roman Catholic seminaries. Czechoslovakia has 4,336 parishes but only 3,175 priests, said the cardinal, and the number has been declining since 1950, when the government shut most of the seminaries.

The government continues to assert it is ready and willing for an accord with the church, and there have been some small signs lately interpreted as good will gestures from the state. In addition to the slight rise in the number of candidates admitted to seminaries, the repression of clergymen has reportedly eased somewhat. No Catholic priests are currently in jail, according to both Tomasek and Janku, following the release in January of three members of the Franciscan order from Liberec in northern Bohemia who were imprisoned in November on a charge of undermining state supervision of the church by holding private masses and theology lessons.