Pope Leo on Tuesday criticized the governor of the U.S. state of Illinois for signing a bill to allow some adults with a terminal illness to end their own lives with medical help, in an unusual political intervention by the church leader.

Leo, the first US pope, told journalists outside his residence in Castel Gandolfo, Italy, that he was "very disappointed" in Governor JB Pritzker for signing the measure.

"Unfortunately ... he decided to sign that bill," said the pope, responding to a question about the measure. "I'm very disappointed about that."

Leo, originally from Chicago, met at the Vatican with Pritzker last month and said he "very explicitly" spoke with the governor about the bill.

The pope, leader of the world's 1.4 billion Catholics, usually refrains from commenting on local political issues.

The Illinois bill, which takes effect next September, gives terminally ill adults with a prognosis of six months or less the option to request a medical prescription to end their lives.

The Catholic Church teaches that life is sacred from conception until natural death. It opposes abortion, capital punishment and assisted dying measures.