Johnson said Monday he doesn't think it is right to "use the process of diplomatic immunity for this type of purpose." The prime minister says he will raise the issue with the White House if necessary.
Johnson urged the woman to return to the U.K. to face investigation. The crash on Aug. 27 killed 19-year-old Harry Dunn after his motorcycle collided with a car near RAF Croughton, a British military base near Oxford. The base is home to a signals intelligence station operated by the U.S. Air Force.