A married African archbishop who has been excommunicated from the Catholic Church has spurred Pope Benedict XVI to convene a summit Thursday on the celibacy requirement for clergy, although the Vatican insists the policy is not open for discussion.

The Vatican's announcement of the meeting of top cardinals at the Holy See said it would examine the implications of the "disobedience" by Zambian Archbishop Emmanuel Milingo.

The Vatican said it would issue a detailed statement, likely late in the day, after the one-day summit.

Milingo incurred automatic excommunication in September when he ordained four married American men as bishops in defiance of the Vatican.

He already had drawn the Vatican's ire in 2001, when he took a South Korean woman as his wife in a group wedding ceremony of the Unification Church of the Rev. Sun Myung Moon.

The prelate is thinking big in his campaign to have the Church to drop the demand that clergy be celibate. He is hoping to draw some 1,000 married Catholic priests to a Dec. 8-10 gathering in the New York City area.

The Holy See has stressed that the summit Thursday would not open up debate on the celibacy requirement, but would instead examine requests for dispensation made by priests wishing to marry and requests for readmission by clergy who had married in recent years. It cited no numbers.

A meeting of bishops from around the world at the Vatican last year rejected suggestions that the celibacy requirement be dropped for priests. Proponents argue that allowing men to marry in the priesthood could help relieve a shortage of clergy in many parts of the world.

A leader of a U.S. organization of married priests said Wednesday there were about 100,000 married priests worldwide. Stuart O'Brien, a board member of the Massachusetts-based Corpus, said that he did not expect any changes to come out of the Vatican summit, even though "Milingo has their attention."

Referring to an estimated 25,000 men who left the active priesthood in the United States to marry, O'Brien said from the United States in a telephone interview: "I don't think that Rome will ever open the door to them."

Louise Haggett, head of the advocacy group Citi ministries (for Celibacy is the Issue), contended that while decades ago, priests seeking dispensations "usually received it within a year," since the 1978-2005 papacy of John Paul II the waiting time has stretched to years.

"There are a lot of priests today who don't even bother to put in a request," Haggett said by phone from her base in Maine.

When Milingo was excommunicated, several Vatican watchers said the Holy See was worried about the possibility that the archbishop, with the power to ordain bishops and priests, could start a schism.

The Vatican requires celibacy of priests ordained under the Latin rite, although married men can become priests in the Eastern rite. The Vatican has also accepted some married Anglican priests who came over to the Catholic fold.

"What I think will eventually happen is that they (the Vatican hierarchy) will change, and they will allow (married) men of virtue to be ordained, older men, maybe deacons, who have proven themselves in parish work," O'Brien said.

Several bishops at the Vatican gathering last year raised the possibility that married men of proven virtue, known in Latin as "viri probati," could be ordained, but that idea was ruled out.