Rome (CNN)Pope Francis opened a highly contentious three-week summit Sunday that could potentially clear the way for some married men to become Catholic priests.
The meeting -- which focuses on environmental and religious issues in the Amazon region -- will take up the question of whether some respected married elder men could be ordained to help overcome a shortage of priests in remote areas in the region.
If approved, it would be a first for the Catholic church and overturn centuries of tradition of a celibate priesthood.
That possibility has caused outrage among Conservative groups who have been protesting with prayer vigils after American Cardinal Raymond Burke and Bishop Athanasius Schneider of Kazakhstan called for "a crusade of prayer and fasting" for 40 days throughout the meeting.
Earlier this week, some 200 Catholics, calling themselves a "spiritual army" stood in formation, rosaries in hand, under the statue of St. Michael the Archangel near the Vatican, to pray for the meeting, also called a Synod.
The battle over ordaining married men may not turn out to be as contentious as some fear, however.
Canadian Cardinal Marc Ouellet, who heads the Vatican's powerful office for bishops and will be voting in the synod, said he is leaning against the proposal.
"I am skeptical, and I think I am not the only one," Ouellet said at a news conference in Rome on Wednesday.
"There is someone above me who is even more skeptical who has authorized the debate and that's OK," he said, in an apparent reference to Pope Francis.
Conservatives are not the only groups dissatisfied with the meeting.
Catholic women's groups, including nuns, have also been protesting with signs in front of the Vatican, demanding the right to vote in the gathering.
A total of 185 men, consisting of priests and bishops, will be voting on the proposals. A group of 35 women, mostly nuns, will be participating, but they do not have the right to vote.
The meeting takes place behind closed doors for three weeks. Voting members each have an opportunity to speak, usually for about 10 minutes each, on topics related to the agenda.
The agenda, called by its Latin name the "Instrumentum Laboris," or "working document," consists of 147 points, which are condensed into a final document and voted on at the end of the Synod by a "yea" or "nay" vote.
Point 129 of the Instrumentum Laboris contains the suggestion that, "the possibility of priestly ordination be studied for older people, preferably indigenous, respected and accepted by their community, even if they have an existing and stable family, in order to ensure availability of the Sacraments that accompany and sustain the Christian life."
Included in point 129 is the question of the role of women.
"Identify the type of official ministry that can be conferred on women, taking into account the central role they play today in the Church in the Amazon."
Proposals approved by the meeting will be sent to Pope Francis for a final decision.