Pope John Paul II strongly defended the Vatican's recent controversial condemnation of the Marxist elements of liberation theology today, saying that the church, committed to help the underprivileged, must protect the poor from "illusory and dangerous" ideologies.

The pontiff said that spiritual poverty, such as that existing under totalitarian regimes, is equally important and warned once again that the Holy See will not accept doctrines that "reduce the evangelical message to abstract sociopolitical and economic categories."

And in warning against "isolationist" or "centrifugal tendencies" within the church, John Paul appeared once again to be putting on notice priests and theologians whose positions do not coincide fully with his conservative doctrine.

At the same time, however, the pope, who spoke for 45 minutes in a year-end address to the cardinals of the Roman Curia, said that "contrary to some distorted impressions," recent documents on liberation theology issued with papal authority by the Sacred Congregation for the Doctrine of the Faith should be viewed as an "authoritative confirmation" of the Roman Catholic Church's commitment to the poor.

". . . It not only does not oppose a choice in favor of the poor, but rather it represents an authoritative confirmation of that choice , at the same time clarifying and deepening it," the pontiff said of the "Instruction Regarding Certain Aspects of Liberation Theology," released Sept. 3 by the head of the congregation, Cardinal Joseph Ratzinger.

The Vatican's sharply criticial attitude on liberation theology, a branch of theology popular in the Third World that often uses elements of Marxist thought to preach the need for social change, has raised concern among many progressive clerics in Latin America and elsewhere that the church will neglect economic and social issues in underdeveloped areas.

But Vatican sources said today that liberation theology and the broader question of the church's relationship to the world's underprivileged was a priority issue for the pope. The subject of liberation theology also was discussed at a meeting of Curia cardinals yesterday at which the pope presided. The sources said that participants came away with the idea that John Paul is likely to release a major document -- possibly an encyclical -- on the subject in the near future.

The pope has hinted several times in recent months that he believes the "Popolorum Progressio" ("The People's Progress") encyclical issued by Pope Paul VI in 1967 ought to be updated.

That encyclical focused the church's attention on the underdeveloped people and areas of the world and opened the way to political involvement by many progressive-minded clerics because it stated that revolt was possible in societies with social structures that could be called permanently oppressive.

The pope has said conditions in the world have changed significantly since then, and he recently was echoed by Cardinal Ratzinger, believed to be close to the pope on doctrinal issues. Ratzinger said in an interview with a conservative Catholic review that the time had come for a "restoration" that would correct some of the imbalances caused by the Second Vatican Council in the early 1960s.

When Ratzinger presented the liberation theology document in September, he and other Doctrine of the Faith officials said there would be a second document later that would talk about liberation theology's "positive" aspects.

This was believed to have been promised to assuage the disappointment felt by many Latin American clerics who believe liberation theology has been an important contribution.

But Vatican sources now say that the pope himself will be handling the theological sequel, one that will put major emphasis on the problem of the world's poor.

The Doctrine of the Faith Congregation, on the other hand, will make its own views on liberation theology clearer when it makes a decision on the case of the Rev. Leonardo Boff, a Brazilian liberation theologian. On Sept. 7 Boff was interrogated by Ratzinger and other congregation officials about his views and writings. At the time Boff described the meeting as a "cordial exchange," but the congregation has yet to decide what, if any, action to take against him.

In his speech today, the pope stressed his social concerns by saying "I take this occasion to reaffirm that the efforts for the poor constitute a dominant concern of my apostolic actions, a constant thought in my daily service to the people of God."