VATICAN CITY, Feb. 26 - The Vatican has reined in a Jesuit theologian, declaring that his book on religious pluralism contained ``notable ambiguities'' that could lead a reader to ``erroneous or harmful positions.''

The statement Monday by the powerful Congregation for the Doctrine of the Faith followed a nearly two-year investigation of the book by the Rev. Jacques Dupuis, a 77-year-old Belgian professor at the Gregorian University in Rome.

It was further evidence that the Vatican will be vigilant that theologians and other Catholics correctly describe orthodox Catholic beliefs, and do not water them down out of their liberalism or to avoid offending non-Catholics.

The Vatican statement said Dupuis had accepted what the church calls a Notification ``intended to safeguard the doctrine of the Catholic faith from errors, ambiguities or harmful interpretations,'' and committed himself to including the it in any future editions of the book. Dupuis, reached at his university office, said he would withhold any comment until Tuesday.

The Vatican's statement is likely to fuel a debate over attempts by some in the church to find common ground with other denominations and religions.

When the Vatican in September reaffirmed the primacy of the Roman Catholic church over other religions, leaders of several denominations expressed dismay that the Vatican was changing course on efforts for dialogue with non-Catholics.

Pope John Paul II has since stressed such dialogue efforts will continue, but he has not disowned the September document from the Congregation for the Doctrine of the Faith, which is headed by the conservative German Cardinal Joseph Ratzinger.

Monday's statement said the pope ``confirmed'' the Notification regarding Depuis on Jan. 19 and ordered its publication.

Dupuis' book, published in 1997, is called ``Toward a Christian Theology of Religious Pluralism.''

The Vatican statement recognized the author's ``attempt to remain within the limits of orthodoxy,'' his willingness to provide clarifications and his desire to remain faithful to church doctrine.

But it said the congregation ``found that his book contained notable ambiguities and difficulties on important doctrinal points'' on salvation and the Catholic church.

"These points concerned the interpretation of the sole and universalsalvific mediation of Christ, the unicity and completeness of Christ'srevelation, the universal salvific action of the Holy Spirit, theorientation of all people to the church, and the value and significanceof the salvific function of other religions," it said.

In a letter addressed to all the members of the Society of Jesus,the largest Catholic religious order, the Jesuit General, the Rev. PeterHans Kolvenbach, praised Dupuis for his work in "a terrain that isdogmatically fundamental for the future of interreligious dialogue."

Kolvenbach said the theologian had tried to "remain within theCatholic faith" in his thinking "without always succeeding," and hecommended Ratzinger's "long and important" doctrinal examination ofDupuis' book.

With the help of the "doctrinal orientation" of the Congregation forthe Doctrine of the Faith, Kolvenbach wrote, "We hope that FatherJacques Dupuis will be able to continue in his pioneering work in thefield of interreligious dialogue."

Ratzinger said the Notification "is not meant as a judgment" onDupuis' subjective thought "but rather as a statement of the church'steaching on certain aspects of the above-mentioned doctrinal truths anda refutation of erroneous or harmful opinions, which, prescinding fromthe author's intentions, could be derived from reading the ambiguousstatements and insufficient explanations found in certain sections ofthe text."

The Notification opened with the statement that "it must be firmlybelieved that Jesus Christ, the son of God made man, crucified andrisen, is the sole and universal mediator of salvation for allhumanity."

"It is consistent with Catholic doctrine to hold that the seeds oftruth and goodness that exist in other religions are a certainparticipation in truths contained in the revelation of or in JesusChrist," it said.

"However, it is erroneous to hold that such elements of truth andgoodness, or some of them, do not derive ultimately from thesource-mediation of Jesus Christ."

"It must be firmly believed," the Notification concluded, "that thechurch is sign and instrument of salvation for all people. It iscontrary to Catholic faith to consider the different religions of theworld as ways of salvation complementary to the church."