The Holy Father is working with determination to promote the necessary conditions for a world free of nuclear weapons, as he reiterated last March in a message addressed to the United Nations Conference, convened for this purpose.

http://w2.vatican.va/content/francesco/en/messages/pont-messages/2017/documents/papa-francesco_20170323_messaggio-onu.html

Therefore, an important conference will be held next week, “Perspectives for a World Free from Nuclear Weapons and for Integral Development”, organized by the Dicastery for Promoting Integral Human Development. However it is false to speak of mediation on the part of the Holy Father.