Mr Johnson said Mr Obama showed black people they "can win"
London Mayor Boris Johnson has endorsed US presidential candidate Barack Obama, saying a win for him would be a "fantastic boost" for black people.
Mr Johnson said the Democratic White House hopeful could do "wonderful things for the confidence of black people around the world".
A victory for Mr Obama in November's US election would show that "they can win", he told Square Mile Magazine.
Mr Johnson also said being mayor felt like being a "bounding panther".
Mr Obama visited London last week as part of his European tour.
Mr Johnson was asked whether, in the light of fears of knife crime, a win for Mr Obama would "have a beneficial influence on the self-image of some of London's black male youth".
He replied: "I was looking at him on the news and just thinking what an amazing moment this is... watching his speech in Berlin and thinking what a critical moment this is for America and for attitudes towards what they can achieve amongst the black community.
"If Barack Obama can do it, it will be the most fantastic boost, I think, for black people everywhere around the world...
"I think [Republican candidate] John McCain has many, many wonderful qualities... but I think a Barack Obama victory would do fantastic things for the confidence and the feelings of black people around the world - that they can win."
Asked by Square Mile's editor, Martin Deeson, if he endorsed Mr Obama, he said: "Yes."
Mr Johnson was elected London mayor in May, replacing Labour's Ken Livingstone, who had held the post for eight years.
Questioned as to whether he was finding the job hard, he said: "I am full of fire. I am like a greased bounding panther.
"My legs are steel springs and every day I get out of bed and I beat my chest. Every morning I am full of wonderment that the people of London have done the honour of making me their mayor. I really am."