ROME — Days after a tentative nuclear deal was struck between Iran and the P5+1 nations, including the United States, a senior US arms control official described the Vatican as an important partner in non-proliferation efforts.

“The Church is a natural leader in the arena of nuclear disarmament,” said Rose Gottemoeller, US undersecretary of state for arms control and international security, during a Friday meeting with journalists at the American embassy to the Vatican.

Gottemoeller said she has great regard for Pope Francis and the commitment he’s conveyed on nuclear disarmament, adding that one of the most influential documents ever written on the subject is Pacem in Terris, written by Pope John XXIII in 1963.

“This isn’t a new thing for the Vatican in any way,” Gottemoeller said.

She was in Rome as part of a broader diplomatic mission to visit countries that are signatories of the Non-Proliferation Treaty that went into force in 1970 with the objective of preventing the spread of nuclear weapons, promoting cooperation in the peaceful uses of nuclear energy, and achieving nuclear disarmament.

As happens every five years, the pact is subject to revision during an April 27-May 22 review conference in New York, where Gottemoeller said the Vatican will be an “active participant.”

Pope Francis recently mentioned the Iran nuclear deal reached in Lausanne, Switzerland, in his Easter address, saying he hoped it would be “a definitive step toward a more secure and fraternal world.”

Gottemoeller said she was “excited and very glad” for the pope’s near-endorsement of the pact, which has drawn criticism from some Republicans in the US Congress.

On the influence of grassroots Catholic activists on nuclear disarmament, Gottemoeller said that “we look upon the non-governmental groups as important partners, even if we don’t always agree,” because “we believe we’re moving in the right direction.”

She said the Obama administration worked very close with faith groups, not only the Catholic Church, but also Evangelical leaders, with regard to the START treaty in 2010.

“[Religious groups] are important partners,” Gottemoeller said. “They’re by no means adversaries.”

Drawing on both Catholic social teaching and the legacy of previous popes, Francis has been outspoken against nuclear weapons during the first two years of his reign.

In December, Francis called nuclear weapons a global problem affecting all nations, threatening “future generations and the planet that is our home.”

“A global ethic is needed,” the pontiff said, “if we are to reduce the nuclear threat and work towards nuclear disarmament.”

Calling the humanitarian consequences of nuclear weapons a source of “unnecessary suffering” beyond their mass-killing potential, Francis said that “nuclear deterrence and the threat of mutually assured destruction cannot be the basis for an ethics of fraternity and peaceful coexistence among peoples and states.”

Although the Vatican will actively participate in the New York summit, there has been some criticism.

Speaking recently at the United Nations, Filipino Archbishop Bernardito Auza, the Holy See’s ambassador to the UN, questioned the slow implementation of a treaty “so important for our mutual security.”

Madelyn Creedon, principal deputy administrator for the US National Nuclear Security Administration, also present at the media briefing in Rome, said the United States is dismantling 300 nuclear weapons a year, “almost the equivalent of one a day.”

Creedon said that the process is slow because it’s technically complicated and there’s only one facility to disarm the more than 30,000 nuclear weapons developed by the US before signing the treaty.

The Vatican clearly expects more.

“In keeping our focus on nuclear weapons and the strengthening of the Non-Proliferation Treaty, we should not neglect our larger objective of a world less reliant on the use of force,” Auza said last October.

Gottemoeller and Creedon will continue their April 9-17 tour with meetings on international security issues with their counterparts in Poland, Latvia, the Baltic States, Lithuania, and Estonia.