Iran accused the U.S. on Friday of using "forged documents" and relying on subterfuge to make its case that Tehran is trying to build a nuclear weapon, according to a confidential letter obtained by The Associated Press.

The eight-page letter — written by Iran's chief envoy to the U.N. nuclear agency in Vienna — denounces Washington's allegations against the Islamic Republic as "fabricated, baseless and false." The letter does not specify what documents Iran is alleging were forged.