U.S. President George W. Bush was expected to speak on Tuesday about the need for multinational diplomacy in his final address to the UN General Assembly in New York.
Bush, who has often criticized the UN over the past seven years, was scheduled to speak for 15 minutes as a new session of the assembly gets underway.
Other speakers at the UN on Tuesday include French President Nicolas Sarkozy and Iranian President Mahmoud Ahmadinejad.
In the past, Bush has said the UN bureaucracy is costly and huge and the UN itself is indecisive in the face of serious world problems.
Ahmadinejad spoke to the UN last year, but his presence caused a stir with thousands protesting outside the building. The U.S. delegation walked out when he rose to speak.
Ahmadinejad told National Public Radio in the U.S. in an interview to be broadcast on Tuesday that he is not interested in having a confrontation with the U.S. and would like diplomatic relations to improve between the two countries.
"We do not have confrontations with anyone," he said. "The U.S. administration interferes, and we defend ourselves."
Ahmadinejad, however, said at a military parade on Sunday that Iran would defend itself were any country to attack its nuclear facilities.
"If anyone allows himself to commit even a tiny offence against Iran's legitimate interests, borders and sacred land, our armed forces will break his hand before he pulls the trigger," he said.
The vice-president of Sudan and leaders from Georgia, Lebanon, Kenya, Somalia, France, Liberia and Argentina are also among those to address the General Assembly on Tuesday.