After Ireland voted to legalize abortion in May, will Argentina, another traditionally Catholic country, do the same?
The country's senators will make the decision Wednesday, amid fiercely polarized campaigns on both sides of the hot-button issue.
The bill was passed by Congress's lower house in June by the narrowest of margins, but it is widely expected to fall short of the votes needed to pass in the Senate -- 37 of the 72 senators have made it known they will say no.
If the measure does fail, lawmakers must wait a year to resubmit the legislation.
As the lawmakers settled in for what was expected to be a marathon session that could stretch past midnight, demonstrators on both sides rallied outside Congress.
Abortion rights supporters wore green scarves while anti-abortion activists donned baby blue. A partition was set up to keep them separated.
Scores of buses have brought people into Buenos Aires from other parts of Argentina, city hall said.
Despite the negative projections and strong opposition from the highly influential Catholic Church in the homeland of Pope Francis, abortion rights proponents are not giving up hope.
"We're doing everything so that the initiative passes. We have faith in the street movement," leading campaigner Julia Martino told AFP.
"We believe many senators will show their support when the vote happens."
Currently, abortion is allowed in Argentina in only three cases, similar to most of Latin America: rape, a threat to the mother's life or if the fetus is disabled.
If passed, the bill would legalize abortion during the first 14 weeks of pregnancy and see Argentina join Uruguay and Cuba as the only countries in Latin America to fully decriminalize abortion.
It's also legal in Mexico City. Only in the Central American trio of El Salvador, Honduras and Nicaragua does it remain totally banned.
With the tide seemingly flowing against legalization, abortion rights groups tried to amend the bill to reduce from 14 to 12 weeks the period during which it would be permitted, but that move failed.
What activists can count on, though, is huge support from citizens.
- Question of rights -
Demonstrations were held in Buenos Aires, with other rallies taking place around the world in front of Argentine diplomatic missions.
One abortion rights protester in Buenos Aires, 20-year-old Celeste Villalba, said keeping abortions illegal would not prevent them from happening.
"This debate is whether it should be legal or done in secret. It's not about being in favor of abortion or not," she said.
She said she feared that "social machismo and a patriarchal and retrograde Church" would block adoption of the bill in the Senate.
Various charities estimate that 500,000 illegal, secret abortions are carried out every year in Argentina, resulting in around 100 deaths.
But opponents of abortion are not lacking support and held their own demonstrations.
Priests and nuns have been joined by rabbis, imams and members of other Christian churches to oppose the bill.
One of them, Federico Berruete, a 35-year-old priest, joined anti-abortion demonstrators holding up slogans reading "Life starts at conception."
"There is a big display of faith, a lot of people have turned out for a more humane country. Children about to be born need to be defended," he said.
With such division in the country, one lawmaker from the ruling party, Daniel Lipovetzky, suggested that the matter might end up being put to a referendum. "It's possible that we propose that," he said.
Ireland ended up overturning its own constitutional ban on abortion through a referendum held in May. That dealt a hammer blow to the Catholic Church, which is as revered in Ireland as it is in Argentina.
In mid-June, Argentina's lower house voted in favor by just 129 to 125, thanks in part to the nonetheless anti-abortion President Mauricio Macri's insistence on pushing the bill through the legislature.
The conservative president released a letter Wednesday welcoming the debate and saying this is about more than legalizing abortion or not.
"As a society, it presents a peaceful scenario to promote and carry out change," the president wrote.
Senator Norma Durango from the Justice Party said she would work "until the last minute so that this becomes law," warning that those who vote against the bill would be "responsible for continuing deaths."
The Catholic Church has appointed a bishop, Alberto Bochatey, to handle dialogue with Congress on the issue.
Last month, Bochatey, 62, told AFP that "you cannot make a law to justify the elimination of human life," but said the Church was against locking up those who carried out illegal abortions.
© Agence France-Presse