In the most extensive reshaping of the Obama administration's national security team to date, the president will name Central Intelligence Agency Director Leon Panetta as his nominee to succeed Robert Gates as defense secretary, top U.S. officials said Wednesday. Gen. David Petraeus will be nominated to take over as CIA director, and Lt. Gen. John Allen will succeed Petraeus as head of the U.S-led international military force in Afghanistan, a senior administration official told reporters. In addition, longtime diplomat Ryan Crocker will be nominated as the next U.S. ambassador to Afghanistan, the official said. President Barack Obama will formally announce the changes on Thursday, according to the senior administration official. It is the biggest reshaping of Obama's national security team since he took office in January 2009 and reflects a longstanding plan by Gates to step aside this year. More changes also are coming. Both Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, and FBI Director Robert Mueller are not eligible for renomination for terms that expire this year. Gates will resign effective June 30, assuming Panetta gets confirmed by Congress in time and is ready to start on July 1, according to an administration official and a congressional aide familiar with phone calls Gates was making to legislators and senior staff members. Petraeus will remain in command