It would build on the conference to negotiate the Nuclear Weapons Ban Treaty, which took place in New York in March 2017.
Pope Francis sent a message to that conference saying that the doctrine of nuclear deterrence has become ineffective against 21st century threats like terrorism, asymmetrical conflicts, environmental problems and poverty.
These threats, the Pope stressed, are "even greater when we consider the catastrophic humanitarian and environmental consequences that would follow from any use of nuclear weapons, with devastating, indiscriminate and uncontainable effects, over time and space."
To Pope Francis, the elimination of nuclear weapons is both "a challenge and a humanitarian imperative." The Pope also asked attendees to promote "reflection on an ethics of peace and multilateral and cooperative security that goes beyond the fear and isolationism that prevail in many debates today."
As a permanent observer to the United Nations, the Holy See took part in the negotiations. It was granted the possibility to participate at procedural votes during the negotiations, a right that the Holy See usually does not use.
The Holy See is a founder and member state of the International Atomic Energy Agency (IAEA), and has always praised the developments in nuclear technology while strongly opposing the development of such technology for military purposes.
This was evident in the May 3 remarks of Monsignor Janusz Urbanczyk, the Holy See's representative to the IAEA.
Addressing the first meeting for the 2020 review conference of the Treaty on the Non-proliferation of Nuclear Weapons, he stressed that "the Holy See cannot but lament the fact that the potential devastation caused by the use of nuclear weapons so clearly identified over 40 years ago has not been relegated to history."