The United States will boycott meetings of the UN Conference on Disarmament when Iran takes over the body this month, a U.S. spokeswoman said Monday.
Iran, and any nation facing sanctions for its weapons program, should be "barred" from holding formal UN positions, said Erin Pelton, spokeswoman for the U.S. mission at the United Nations, according to the AFP news agency.
Iran will take over presidency of the disarmament conference from May 27 until June 23 under an alphabetical rotation among the 65 member states.
The conference is struggling to craft a deal on nuclear disarmament, preventing arms from spreading to outer space and halting the development of other weapons of mass destruction.
Iran, meanwhile, faces four rounds of UN sanctions over its nuclear program.
Iran's presidency is "unfortunate and highly inappropriate," said Pelton, according to AFP.
"The United States will not be represented at the ambassadorial level during any meeting presided over by Iran," she stressed.
"The United States continues to believe that countries that are under Chapter VII sanctions for weapons proliferation or massive human-rights abuses should be barred from any formal or ceremonial positions in UN bodies."
Pelton acknowledged that the conference presidency is largely ceremonial with no responsibilities.
She added, however, that "allowing Iran -- a country that is in flagrant violation of its obligations under multiple UN Security Council resolutions and to the IAEA board of governors -- to hold such a position runs counter to the goals and objectives of the Conference on Disarmament itself.”
The International Atomic Energy Agency is responsible for investigating Iran's nuclear program, which western nations say hides a bid to develop a nuclear weapon. Iran denies the charge.
The IAEA conducts regular inspections of Iran's declared nuclear sites and its quarterly reports routinely outline advances in its atomic program in spite of UN Security Council resolutions calling for a suspension.
Its latest report, issued February 21, said that Iran had begun installing at its Natanz plant more advanced centrifuges to speed up uranium enrichment, a process at the heart of the international community's concerns.
Enriched uranium can be used for peaceful purposes but also, in highly purified form, in a nuclear weapon.
Iran's position heading the conference has also angered non-government lobby groups such as UN Watch.
"This is like putting Jack the Ripper in charge of a women's shelter," said Hillel Neuer, head of the Geneva-based UN Watch, announcing that the organization would organize protest events involving Iranian dissidents.
"Iran is an international outlaw state that illegally supplies rockets to Syria, Hizbullah, and Hamas, aiding and abetting mass murder and terrorism," said Neuer.