US President Barack Obama has described as "hateful" and "offensive" the claim by Iran's President Mahmoud Ahmadinejad that most people believe the US government was behind the 9/11 attacks.

In his speech at the UN, the Iranian leader suggested the US government could have "orchestrated the attack to reverse the declining American economy, and its grips on the Middle East, in order to save the Zionist regime".

Obama said it was inexcusable to make such remarks in New York itself, where most of the victims of 9/11 died.

But despite his condemnation, the US president reaffirmed America's commitment to reach out to the people of Iran, who he said had a very different response to 9/11.

Ahmadinejad's speech at the UN General Assembly on Thursday triggered a walkout, BBC reported.