VATICAN CITY (CNS) — Pope Francis “has been a tireless advocate for a world free of nuclear weapons,” said the head of the Comprehensive Nuclear-Test-Ban Treaty Organization.

Lassina Zerbo, the organization’s executive director, spoke to Pope Francis April 22 at the end of the pope’s weekly general audience and said he thanked the pope for the work he’s done “to ban nuclear testing and to rid the world of the abomination of nuclear weapons.”

The pope’s support should encourage other religious leaders to rally their faithful in pushing reluctant nations to sign and ratify the test-ban treaty, Zerbo told Vatican Radio. The eight countries with nuclear technology who have not signed the treaty are: China, Egypt, India, Iran, Israel, North Korea, Pakistan and the United States.

“One should see the disaster that nuclear testing represents,” Zerbo said. “We should consider the 21st century as a century of peace, stability and security, should we take the leadership to that effect.”

“There should be no testing above ground, underground, underwater or in the air,” he added.

Vatican officials have held a number of meetings recently to discuss nuclear disarmament and nonproliferation.

Ahead of the Nuclear Nonproliferation Treaty Review Conference April 27-May 22 at the United Nations, Rose E. Gottemoeller, the U.S. undersecretary of state for arms control and international security, met with officials of the Vatican Secretariat of State, the Pontifical Council for Justice and Peace, and the Pontifical Academy of Sciences.

In addition, Archbishop Bernardito Auza, the Vatican’s permanent observer to the United Nations, hosted a conference “Nuclear Weapons and the Moral Compass” April 9.