Time magazine reported a conversation in January, a few days before the presidential speech, between a top CIA analyst, Alan Foley, and a "a key national security council official", in which Mr Foley objected to including the allegation in the speech.
Robert Joseph, the president's adviser on weapons of mass destruction, denied he was the official who approved the line about British intelligence.
But Time quoted another official as saying: "There was a debate about whether to cite it on our own intelligence. But once the UK made it public, we felt comfortable citing what they had learned."