No, it was not that it would not stand up to scrutiny, which implies the allegation would fall apart upon examination.
To the contrary. The U.S. still feels it is most likely true, but they have not gathered sufficient intelligence to proclaim it via the president. However, Britain has their own sources and they are quite confident that it is true.
Portions of the State of the Union speech draft came to the CIA for comment shortly before the speech was given. Various parts were shared with cognizant elements of the agency for review. Although the documents related to the alleged Niger-Iraqi uranium deal had not yet been determined to be forgeries,