Twelve women who will undergo a ritual on a riverboat today, which they say will make them Roman Catholic priests and deacons, held a press conference last night at Station Square to explain their motives for a ceremony that the Diocese of Pittsburgh calls a cause for excommunication.

The changes they want in the Catholic Church go far beyond women's ordination.

Roman Catholic Womenpriests wants the church to be "non-hierarchical, non-clerical and inclusive," said Patricia Friesen, considered a bishop in the group.

"We do not ask the people ordained by us to make a promise of obedience to the bishop."

One local woman, Joan Clark Houk, 66, of McCandless, is among the eight candidates for priesthood. The others, plus four deacon candidates, are from throughout the nation. This is the fourth such riverboat ceremony held worldwide since 2002.

The Diocese of Pittsburgh has warned that even those who attend as guests to encourage the women will excommunicate themselves. Furthermore, those who have ministry positions in the Catholic Church -- including teachers in Catholic schools -- risk losing their jobs if they attend, the statement warned. Such workers, lay or volunteer, are bound by a rule that says "anyone who publicly supports things which are in opposition to the church is subject to immediate discharge," said the Rev. Lawrence DiNardo, the chief canon lawyer for the diocese.

Last night Jean Marchant, 62, who until last week was director of health care for the Catholic Archdiocese of Boston, said that was the reason that she had only now revealed that she was ordained under a pseudonym on a riverboat in Canada last year. She resigned from the diocese and is now working with other women in the Boston area to open a spirituality center, she said.

An activist on behalf of married priests asked the women how their husbands or partners felt about their new ministry. John Houk said that his wife had been "an occasion of grace for me" throughout their 45-year marriage.

"The concept of celibacy may be right for some people," he said. "But two people can do more than one when they are in partnership with each other. I believe we can be an example of that."