FBI Deputy Director Thomas Pickard will serve as acting director of the agency, Atty. Gen. John Ashcroft said Friday.
Pickard was second in command to Director Louis J. Freeh, who retired Friday after eight years of a 10-year term.
Mueller, U.S. attorney in San Francisco, is the only candidate under consideration, senior administration officials have said. President Bush has asked advisors to expand the search but views Mueller as a strong prospect.
A 26-year FBI veteran, Pickard was assistant director of the bureau's criminal investigation division and its Washington field office. He had been special agent in charge of the national security division in New York, where he supervised the trials of the World Trade Center bombing defendants and the investigation of the TWA Flight 800 explosion.
Pickard worked undercover in the 1979 ABSCAM investigation, in which FBI agents posed as Arab businessmen offering bribes to members of Congress.