The Pope's remarks, at a speech in Castel Gondolfo near Rome, will be seen as an implied criticism of US President Donald Trump, who last month called climate change a "con". Pope Leo also called for greater action from citizens the world over on climate change, saying there was no room for indifference or resignation.

U.S. bishops and the Vatican have strongly called for humane treatment of migrants, citing the Biblical command to “welcome the stranger.”