During the NBC coverage of President Bush's State of the Union address last week, Williams misidentified Obama as Ford, The Hill reported Tuesday.
"I made a silly and honest mistake, and knowing both men I knew instantly what I had done," Williams told The Hill. "I obviously should have corrected it, but the proper time never arose."
Williams said he wrote letters to both men apologizing for his mistake.
The NBC anchor hardly set a precedent, however, The Hill noted.
After last year's State of the Union address, a reporter asked Obama's office why the Illinois Democrat hugged President Bush. Unfortunately, the hugger was Ford.