UNITED NATIONS--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.