The United States criticized Iran’s appointment to a four-week stint as chair of the U.N. Conference on Disarmament, pledging to boycott any sessions presided over by Tehran.

Iran, which is under U.S., E.U., and U.N. Security Council sanctions due to its failure to bring its illicit nuclear program into compliance with the Nuclear Non-Proliferation Treaty, will be tasked with chairing the conference whose agenda includes “the cessation of the nuclear arms race and nuclear disarmament.”

Protesting Iran’s appointment, Erin Pelton, spokeswoman for the U.S. mission to the United Nations, affirmed the U.S. position that “countries that are under Chapter VII (U.N.) sanctions for weapons proliferation or massive human-rights abuses should be barred from any formal or ceremonial positions in U.N. bodies.”

In a May 13 statement, Pelton classified Iran’s chairmanship of the program as “unfortunate and highly inappropriate,” noting that Iran’s proliferation activities directly oppose the objectives of the Conference on Disarmament.

The U.N. Conference on Disarmament is “the world’s sole multilateral disarmament forum,” and its chairs are assigned on a rotating basis. The Conference has been deadlocked since 1998 due to its members being unable to agree on priorities.