Though Iran has condemned the al Qaeda attacks on New York and Washington in the past, this was the third time in a week Ahmadinejad questioned the death toll, who was behind the attacks and how it happened.
"Four or five years ago, a suspicious event occurred in New York. A building collapsed and they said that 3,000 people had been killed but never published their names," Ahmadinejad told Iranians in the holy city of Qom.
"Under this pretext, they (the U.S.) attacked Afghanistan and Iraq and since then a million people have been killed only in Iraq," said Ahmadinejad in the speech broadcast live on state-run television.
On the last anniversary of the attacks, the names of 2,750 victims killed in New York were read aloud at a memorial ceremony there.
Last year, Ahmadinejad raised questions over the September 11 attacks, saying "what caused it, what were the conditions that led to it, who truly was involved" needed to be examined.
In the past, Ahmadinejad has said that the attack was "a result of mismanaging and inhumane managing of the world by the U.S." and it should not be turned into another Holocaust and "be used for slaughtering people."
Although Iran has condemned the U.S. invasions of Afghanistan and Iraq, the campaigns toppled the Taliban and Saddam Hussein, two regional threats to Iran.