Ecuadorean President Rafael Correa has said he will resign if the National Assembly decriminalises abortion as part of a reform of the Penal Code.
Mr Correa, whose term ends in 2017, described himself as a "left-wing, humanist, Roman Catholic".
He said members of his own governing alliance have been pushing for the change.
"They can do whatever they want. I will never approve the decriminalisation of abortion," he said.
Mr Correa has accused many members of his governing bloc of betraying him and trying to push their own agenda by stealth.
"It has cost me more, the betrayals of my own supposed friends, than the acts of my enemies."
"If these acts of betrayal and disloyalty go on, I will tender my resignation," said Mr Correa.
Mr Correa, an economist trained in the United States, first came into power in 2007. He was elected to a third term in February.
He is part of a new wave of left-wing leaders that came into power in Latin America in the last 15 years, following the electoral success of the late Venezuelan president, Hugo Chavez.
Mr Correa has criticised "American imperialism" in the region and in August 2012 offered political asylum to WikiLeaks founder Julian Assange, who is holed up at the Ecuadorean embassy in London.
More recently, Mr Correa has offered asylum to American whistleblower Edward Snowden, former contractor at the US National Security Agency.
The opposition has accused him of attempting to stifle debate and control the media.
A new media law was approved earlier this year by an overwhelming majority at the National Assembly, where Mr Correa's Alianza Pais party has nearly three-quarters of the 137 seats.
The Assembly is now on the second and final stage of debates into changes to the Penal Code.
Among the proposals being examined are tougher prison sentences, of up to 40 years, and specific legislation to deal with crimes against women.
Mr Correa said its members were fully aware of his personal and his party's pro-life stance.
"Where do we say we should decriminalise abortion? On the contrary, our constitution pledges to defend life from the moment of conception," Mr Correa said in an television interview broadcast on Thursday evening.
The death penalty and life sentences are also banned by the South American country's constitution.
Abortion is totally banned or highly restricted in most Latin American countries.