US President Barack Obama described as 'hateful' and 'offensive' the comments by Iranian President Mahmoud Ahmadinejad that some people believed the US government was behind the Sept 11, 2001 terrorist attacks.
'It was offensive. It was hateful - and, particularly, for him to make the statement here in Manhattan, just a little north of Ground Zero, where families lost their loved ones,' Obama said in an interview to BBC Persian TV.
'People of all faiths, all ethnicities who see this as the seminal tragedy of this generation - for him to make a statement like that was inexcusable,' Obama said.
Ahmadinejad said in a speech on Thursday to the UN General Assembly that some 'segments' of the US government 'orchestrated' 9/11 to 'reverse the declining American economy and its grips on the Middle East in order also to save the Zionist regime'.
Delegates from the US and several European countries walked past him and out of the room.
Nearly 3,000 people died on 9/11, including more than 2,700 in New York alone when two hijacked planes crashed into the twin towers of the World Trade Center.
While criticising the Iranian president, Obama said the people of Iran had a very different response to the terrorist attacks.
'There were candlelight vigils, and I think a natural sense of shared humanity and sympathy was expressed within Iran,' he said.
'It just shows once again the difference between how the Iranian leadership and this regime operates and how, I think, the vast majority of the Iranian people, who are respectful and thoughtful, think about these issues.'
European Union foreign policy chief Catherine Ashton on Thursday described Ahmadinejad's claims as 'outrageous and unacceptable'.
'It is for this reason,' she said, 'that all representatives of the 27 nations of the EU walked out of the ... hall.'