All sources spoke on condition of anonymity because the changes haven't been announced by the president.

The changes would probably take effect this summer. Defense Secretary Robert Gates has already said he will leave this year, and the White House wants to schedule Senate confirmation hearings in the coming months.

The officials say Obama is expected to also announce that Lt. Gen. John Allen would replace Petraeus as Afghanistan commander, and that diplomat Ryan Crocker will be the next U.S. ambassador in Afghanistan.