Iranian President Mahmud Ahmadinejad has applied for a U.S. visa to participate in the Nuclear Non-Proliferation Treaty Review Conference from next week, U.S. ambassador to the UN said on Wednesday.

"My understanding is that as of today he has filed an application for a visa," Susan Rice said.

The review conference is held every five years and will be attended by more than 30 foreign ministers.

The United States and other Western countries suspect Iran of developing nuclear weapons under the guise of a civilian nuclear energy program. This is likely to be one of the main focuses of the conference.