WASHINGTON -- President Barack Obama is considering asking Sen. John Kerry (D-Mass.) to serve as his next defense secretary, part of an extensive rearrangement of his national security team that will include a permanent replacement for former CIA director David Petraeus.

Although Kerry is thought to covet the job of secretary of state, senior administration officials familiar with transition planning said, that nomination will almost certainly go to Susan Rice, the U.S. ambassador to the United Nations.

Kerry did not respond to requests for comment.

John Brennan, Obama's chief counterterrorism adviser, is a leading contender for the CIA job, officials said. But if Brennan goes ahead with his plan to leave government, Michael Morell, the agency's acting director, is the prohibitive favorite to take over permanently.

Officials cautioned that the White House discussions are still in the early phases and that no decisions have been made.

Petraeus' resignation last week has complicated plans for the administration's national security and diplomatic teams for Obama's second term.

Rice, one of an inner circle of aides who have been with Obama since his first presidential campaign in 2007, is under fire over the Benghazi, Libya, attack in which U.S. Ambassador Christopher Stevens and three other Americans were killed.

Some GOP lawmakers have suggested she was part of what they suspect was an initial, election-related attempt to portray the attack as a peaceful rally that turned violent, not what the administration now acknowledges was an organized terrorist assault.

Rice's description, days after the attack, of a protest gone wrong was either intentionally misleading or incompetent, Sen. Lindsey Graham (R-S.C.) said Sunday. Rice, he said, "would have an incredibly difficult time" winning Senate confirmation as secretary of state.

But several White House officials said Obama is prepared to dig in his heels over her nomination to replace Hillary Rodham Clinton.

Tommy Vietor, National Security Council spokesman, said the White House would not comment on personnel matters.

The timing of a nomination for Defense Secretary Leon Panetta's successor is unclear. Monday, Panetta said he had no imminent plans to step down. "Who the hell knows," he told reporters en route to Australia, where he was to attend a defense summit with Clinton. "It's no secret that at some point I'd like to get back to California."

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