LONDON, Oct. 16 -- On the day the Vatican said Pope Leo has lung cancer, the Holy See's foreign minister used a London lecture to defend its most criticised habit: talking to leaders it does not endorse.

Archbishop Paul Richard Gallagher, the Secretary for Relations with States and International Organisations, told the lecture on 13 October that successive popes have been condemned for receiving certain political leaders. "Speaking to them is not the same as endorsing them or everything they do," he said, Vatican News reported.

The argument is not abstract. Since July, Gallagher has taken it to both capitals of the Russia-Ukraine war. He ended a five-day mission to Ukraine with a meeting with President Volodymyr Zelensky, and on 25 Augu...