ABOARD THE PAPAL PLANE (AP) — Pope Francis slammed both U.S. presidential candidates on Friday for what he called anti-life policies on abortion and migration, and advised American Catholics to choose who they think is the “lesser evil” in the upcoming U.S. elections.

“Both are against life, be it the one who kicks out migrants or the one who (supports) killing babies,” Francis said. “Both are against life.”

The Argentine Jesuit was asked to provide counsel to American Catholic voters during an airborne press conference en route back to Rome from his four-nation tour through Asia. Francis stressed that he is not an American and would not be voting.

Neither the Republican candidate Donald Trump nor the Democratic candidate Kamala Harris was mentioned by name.

But Francis nevertheless expressed himself in stark terms when asked to weigh in on their positions on two hot-button issues in the U.S. election — abortion and migration — that are also of major concern to the Catholic Church.

Francis has made the plight of migrants a priority of his pontificate and speaks out emphatically and frequently about it. While strongly upholding church teaching forbidding abortion, Francis hasn’t emphasized church doctrine as much as his predecessors.

Francis said migration is a right described in Scripture, and that anyone who doesn’t follow the Biblical call to welcome the stranger is committing a “grave sin.”

He was also blunt in speaking about abortion. “To have an abortion is to kill a human being. You may like the word or not, but it’s killing,” he said. “We have to see this clearly.”

Asked though what to do at the polls, Francis recalled the civic duty to vote.

“One should vote, and choose the lesser evil,” he said. “Who is the lesser evil, the woman or man? I don’t know.

“Everyone in their conscience should think and do it,” he said.

It’s not the first time Francis has weighed in on a U.S. election. In the run-up to the 2016 election, Francis was asked about Trump’s plan to build a wall at the U.S.-Mexican border. Francis declared then that anyone who builds a wall to keep out migrants “is not Christian.”

In responding Friday, Francis recalled that he celebrated Mass at the U.S.-Mexico border and “there were so many shoes of the migrants who ended up badly there.”

Trump pledges massive deportations, just as he did in his first White House bid, when there was a vast gulf between his ambitions and the legal, fiscal and political realities of such an undertaking.

The U.S. bishops conference, for its part, has called abortion the “preeminent priority” for American Catholics in its published voter advice. Harris has strongly defended abortion rights and has emphasized support for reinstating a federal right to abortion.

In his comments, the pope added that on abortion, “science says that in the first month after conception, all the organs of a human being are already there, all of them.”

“Performing an abortion is killing a human being,” he said. "Whether you like the word or not, this is killing.”

However, cells are only beginning the process of developing organs in the earliest weeks of pregnancy. The American College of Obstetricians and Gynecologists says that by 13 weeks, all major organs have formed. For example, cardiac tissue starts to form in the first two months — initially a tube that only later evolves into the four chambers that define a heart.

In other comments, Francis:

— denied a French media report that he would travel to Paris for the December inauguration of the restored Notre Dame Cathedral, saying flat-out he would not be there. But he confirmed he would like to go to the Canary Islands to highlight the plight of migrants.

— tamped down renewed speculation that he might finally return to Argentina later this year, saying he wants to go but that nothing had been decided. He added: “There are various things to resolve first.” Francis hasn’t been home since before the 2013 conclave that elected him pope.

— declared that China was “a promise and a hope” for the Catholic Church and hoped to one day visit.

— called sexual abuse “demonic” and weighed on the latest revelations of assault against a legendary French priest, Abbe Pierre.