Johnson was in New York to promote London before the Olympics and took part in an interview with the veteran talk show host David Letterman.
During the chat Boris admitted that he now regrets saying he won’t run for a third term as Mayor as he admitted his chances of becoming Prime Minster are about as likely “as being reincarnated as an olive". But the mayor said he could "technically" be US president after being born in New York.
He also told the broadcaster about his Boris Bike scheme, soon to be taken up by the American city, and the investment to the transport system he has been behind.
But during the light-hearted interview, Letterman seemed more interested in his haircut.
"How long have you been cutting your own hair?" he joked.