Roman Catholics who last fall challenged the church's position on abortion have organized in defense of the 24 nuns threatened with expulsion from their orders for signing an advertisement calling for dialogue on the issue.

In two days of closed-door meetings at a Chicago retreat house over the weekend, about 40 of the 97 signers of the ad laid plans for a public campaign supporting the right to dissent from church teaching. They also pledged efforts to expand the perception and role of women in a church governed by a male hierarchy and clergy.

The group plans public hearings here March 4 and 5 on women's issues from a Catholic perspective. A committee of Catholic bishops assigned to draft a pastoral letter on women and the church will be holding closed hearings then.

The dissenters plan to seek non-Catholics' support for their call for dialogue and a right to dissent from official church views.

The activities stem from a controversy generated in October when a group of Catholics, most of them academics, ran a full-page ad in The New York Times calling for "pluralism" and dialogue on the church's position that abortion is morally wrong in all cases.

The dispute came at the height of an election-year controversy involving New York Archbishop John J. O'Connor over the obligation of Catholic politicians to work for legislation outlawing abortion.

In late November, the Vatican directed the superiors of 27 members of religious orders who signed the ad to recant or face possible expulsion from their orders. Two of the men in religious orders and one parish priest have recanted, but none of the women has indicated she will.

Marjorie Maguire of Milwaukee, one of the lay signers of statement, said "there was no talk about retraction" at the meeting in Chicago, although she noted that such considerations were not the focus of the sessions.

"They were saying, 'Where do we go from here?' " she said. "It was not like a defiance meeting where everybody is saying, 'No, we are not giving in.' "

Also over the weekend, a professional academic association, the Society of Christian Ethics, unanimously adopted a resolution on the controversy.

Noting that some of its members "are the object of punitive actions from their church authorities," the ethicists said that "in any processes that might issue in disciplinary action, the accepted principles of academic freedom and due process of law must apply."

Maguire, a member of the group, said she was not aware of any threats against lay Catholics who signed the October statement, although a number of them teach at Catholic institutions.

Participants at the Chicago meeting, who included about 20 of the nuns threatened with Vatican discipline, named a steering committee to coordinate the new campaign.

One of the first efforts of the panel, which includes 10 signers of the ad, will be to draft a statement stressing the right of dissent within the church. The proposed statement will be circulated in an effort to elicit wide support, and eventually will be published.

The controversy involving the nuns is expected to be protracted. The Vatican has not given a deadline for compliance.

Meanwhile, the women's religious superiors, who have met several times, have consulted canon lawyers about due-process procedures in the church's revised code of canon, or church, law that might apply.