The Vatican is to host a high-level international conference on nuclear weapons next month.
It is set to be dominated by the escalating tension between the US and North Korea over the communist state's nuclear ambitions.
Nobel peace laureates and top United Nations and NATO officials will take part in the meeting, which will include an address by Pope Francis.
The Argentine pontiff is "working hard to promote the conditions for a nuclear-free world", according to Vatican spokesman Greg Burke.
He denied press reports that the conference represented a mediation effort by Pope Francis.
The meeting will include the personal testimony of Masako Wada, a survivor of the atomic bombing of Nagasaki in Japan.
Archbishop Silvano Tomasi, the Holy See's permanent observer to the UN, who often speaks for the pope on the nuclear issue, said it was "clear we are facing a real risk of the use of atomic weapons".
It could happen "by chance, by choice, or because those sitting in the rooms with the buttons are unbalanced," he said in an interview with La Repubblica daily.
"Working to make sure our security is guaranteed not by weapons of mass destruction, but by the fact that nobody can use them, has become increasingly urgent," he added.
North Korea recently sparked global alarm by conducting a sixth nuclear test and test-launching missiles capable of reaching the US mainland.
US President Donald Trump and the North's young ruler Kim Jong-Un have traded threats of war and personal insults.