Mr. Varadkar was the fresh face of leadership last year when, at 38, he became Ireland’s youngest prime minister. He is the first Irish prime minister to have a nonwhite parent, and he came out as gay in the run-up to the successful 2015 initiative to legalize same-sex marriage.

Previously, while a junior member of Parliament, Mr. Varadkar had taken a number of socially conservative positions. In 2010, he spoke against legalizing abortion for victims of rape, saying it would lead to abortion on demand. In 2009, he opposed changing the law to allow gay couples to adopt children.

But during his Saturday morning interview, Mr. Varadkar said that his beliefs had evolved since 2014, when he had described himself as “pro-life.”

“I think sometimes that term ‘pro-life’ and ‘pro-choice’ can be misunderstood. You know, I think even people who are in favor of abortion in certain circumstances are pro-life,” he said. “I still believe in life, but I understand that there are circumstances in which pregnancies can’t continue.”

He added: “Every single person I know who says they are pro-choice believes in some sort of restriction. These terms pro-life and pro-choice don’t really comprehend the complexity of this issue, which is a very private and personal one and one I think contains a lot of gray areas.”

If repealed, the constitutional ban would be replaced by legislation regulating abortion, most likely permitting it under at least some circumstances. Mr. Varadkar’s government says it will disclose its proposed legislation before voters act on the constitutional provision, but it has yet to formally agree on what the measures might be. An all-party parliamentary committee voted in December in favor of permitting unrestricted abortion up to the 12th week of pregnancy, and later in cases of rape, incest or fatal fetal abnormality.