UNITED NATIONS (AP) — The 191 parties to the Nuclear Nonproliferation Treaty have decided to postpone a conference to review its implementation because of the coronavirus pandemic, the United Nations said Friday.

The treaty is considered the cornerstone of global efforts to prevent the spread of nuclear weapons and the parties hold a major conference every five years to discuss how it is working. The meeting had been scheduled for April 27-May 22 at U.N. headquarters in New York.

U.N. spokesman Stephane Dujarric said the review conference will be held “as soon as the circumstances permit, but no later than April 2021.”

The U.N. said earlier this week that the conference was likely to be postponed, but the conference president-designate, Ambassador Gustavo Zlauvinen of Argentina, wanted to consult governments that are parties to the treaty.

The Nuclear Nonproliferation Treaty, which reached its 50th anniversary March 5, is credited with preventing the spread of nuclear weapons to dozens of nations. It has succeeded in doing this via a grand global bargain: Nations without nuclear weapons committed not to acquire them; those with them committed to move toward their elimination; and all endorsed everyone’s right to develop peaceful nuclear energy.

The 191 state parties include every nation except India, Pakistan and North Korea, which possess nuclear weapons, and Israel, which is believed to be a nuclear power but has never acknowledged it.

Members try to agree on new approaches to problems, not by updating the treaty, which is difficult, but by trying to adopt a consensus final document calling for steps outside the treaty to advance its goals. That has also proven difficult at recent review conferences,

U.N. disarmament chief Izumi Nakamitsu warned earlier this month that the specter of an unbridled nuclear arms race is threatening the world for the first time since the 1970s, the height of the Cold War between the United States and the former Soviet Union.

She didn't name any countries but she was clearly referring to the United States and Russia, and possibly China, when she told the U.N. Security Council that "relationships between states — especially nuclear-weapon states — are fractured."

“So-called great power competition is the order of the day.” Nakamitsu said.

Russia-U.S. relations have been at post-Cold War lows since Moscow's 2014 annexation of Ukraine's Crimea.

Russia and the U.S. clashed at the Security Council meeting where Nakamitsu spoke but they joined in supporting a statement saying the treaty "remains the cornerstone of the nuclear nonproliferation regime and the foundation for the pursuit of nuclear disarmament and the peaceful uses of nuclear energy."

The council resolved to advance the treaty's goals and underlined its essential role “in the preservation of international peace, security and stability as well as the ultimate objective of a world without nuclear weapons.”