The meeting is scheduled for September 24 during the annual General Assembly gathering of world leaders in New York.
According to Reuters, UN officials said that until Monday Ahmadinejad had been the only head of state due to attend the meeting, which the world body had said would be at "ministerial or higher" level. They had since learned that he would not be coming.
UN Secretary-General Ban Ki-moon told Reuters in an interview on Tuesday, "I understand that he [Ahmadinejad] is not going to participate in that meeting."