The nation's Roman Catholic bishops yesterday called U.S. support for the Nicaraguan contras "morally flawed" and endorsed the Central American peace plan offered by Costa Rican President Oscar Arias Sanchez.

"Only a political solution can finally be successful in Nicaragua as in Central America generally," said the statement adopted by the National Conference of Catholic Bishops. "There is no politically or morally acceptable military solution."

In the final session of the conference's annual meeting here, the bishops overwhelmingly approved the Central America policy statement by voice vote, despite spirited efforts by conservative prelates to shelve it.

"This is a delicate moment," said Cardinal Bernard Law of Boston in urging rejection of the 5,000-word document. "The place for discussion, at this point, must be in the nations of the {proposed} agreement." He warned that "one or another party would be able to manipulate our statement for propaganda purposes."

"To say the system we have of aiding the contras is wrong is to aid the Sandinistas," Archbishop Philip Hannan of New Orleans agreed.

But Archbishop Roger Mahoney of Los Angeles, a member of the drafting committee, said the statement reflected "the concerns of the bishops of the churches of Central America," who had approved the document's first draft. "I think we owe the bishops and the churches of Central America . . . our support," Mahoney said.

"We are letting the bishops of the Central American church down if we say nothing," said Bishop Nicholas D'Antonio, a former missionary bishop in Honduras who now works in New Orleans. Central Americans will wonder, he

said, " 'What's happening to the {American} bishops? Did the contras get them, too?' "

The statement called economic questions "the most urgent polity issues facing Latin America today . . . . The return to democracy in the major countries of South America, as well as the advances of democratic rule in Central America, are put at greatest risk by the hemispheric crisis of growth and the external debt problem."

The same statement gave tacit support to the sanctuary moment, urging American Catholics "to increase their already commendable assistance to all refugees, asylum seekers and displaced persons in need," whether or not the refugees "fulfill the legal requirements of the present legislation for legalization."

In other business:Archbishop John May of St. Louis, conference president, said a position paper on AIDS would be mailed to the bishops and made public "as soon as it can be printed." The drafting committee did not complete the document in time for it to be presented here. A proposal that would establish guidelines to help thrash out differences between bishops and theologians got a generally hostile reception from the bishops.

The document, drafted in cooperation with the Canon Law Society and the Catholic Theological Society of America, recommends procedures for resolving disputes before they become crises. It underscores the theologians' right to critical inquiry but their obligation to pursue their questioning within the faith.

"It is seriously flawed and needs to be redone," said Archbishop J. Francis Stafford of Denver, who read from a "three-page, single-spaced" line-by-line indictment of the document until he was cut off at the end of his allotted 10 minutes.

The statement, the last item on the agenda, was not put to a vote because the conference had lost its quorum. It will come before the conference at its next scheduled meeting in June.