The United States and Iran traded sharp accusations at the United Nations on Monday, highlighting deep divisions over Tehran's nuclear program and its appointment as a vice president of the latest review conference of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).

The 11th NPT Review Conference opened at UN headquarters in New York, where 34 vice presidents were nominated by different groups. Conference chair Do Hung Viet, Vietnam's ambassador to the UN, said Iran's nomination came from the Non-Aligned Movement and other states.

Christopher Yeaw, assistant secretary at the US Bureau of Arms Control and Nonproliferation, called Iran's selection an "affront" to the treaty. He said it was "indisputable" that Iran has shown "contempt" for its non-proliferation obligations and has failed to fully cooperate with the International Atomic Energy Agency over outstanding questions about its nuclear activities.

Describing the appointment as "beyond shameful," Yeaw argued it undermines the credibility of the conference and urged participants to act with greater responsibility. He added that Washington "categorically rejects" any leadership role for Iran on nuclear non-proliferation issues.

Iran strongly rejected the criticism. Reza Najafi, Tehran's ambassador to the International Atomic Energy Agency, dismissed the US remarks as "baseless and politically motivated."

"It is indefensible that the United States – the only country ever to have used nuclear weapons, and one that continues to expand and modernize its arsenal – seeks to position itself as an arbiter of compliance," he told the meeting.

Najafi also accused the United States and Israel of carrying out military actions against Iran and its safeguarded peaceful nuclear facilities, calling such moves violations of international law and "a direct attack" on the global non-proliferation regime.

The NPT, which entered into force in 1970, remains the cornerstone of global efforts to prevent the spread of nuclear weapons and promote disarmament. Its review conferences, held every five years, assess implementation and set the direction for future cooperation. The current session is scheduled to run through May 22.

Opening the conference, UN Secretary-General Antonio Guterres warned of a growing erosion of arms control frameworks and a renewed rise in nuclear risks. He said the world is facing a "collective amnesia" about the dangers posed by nuclear weapons and urged all states to honor their commitments, stressing that disarmament and non-proliferation remain "the only true path to peace."