Despite those admonitions, at least 53 member states of the United Nations have signed the treaty since a ceremony to start the ratification process was held at the General Assembly on Sept. 20. While only three — Guyana, the Vatican and Thailand — had formally ratified the treaty as of Friday, others are expected to do so in the coming year.

The treaty will go into effect 90 days after 50 United Nations member states have formally ratified it.

Delegates representing two-thirds of the General Assembly’s 193 members participated in the treaty negotiations.



“We have received this news with so much joy,” Elayne Whyte Gómez, the Costa Rican ambassador to the United Nations in Geneva, who was the chairwoman of the negotiations, said in a telephone interview. “Every year there should be at least one happy event to give us hope, and this was it.”

She said ICAN’s work “represented efforts by civil society activists who approached governments around the world and maintained the momentum of the negotiations to keep them going.”

The prize came as a surprise to Beatrice Fihn, the executive director of ICAN, which has a three-person office in Geneva. She said at a news conference that she had thought at first that the congratulatory telephone call from the Nobel committee was fake.

Under the agreement, all nuclear weapons use, threat of use, testing, development, production, possession, transfer and stationing in a different country are prohibited.