President Barack Obama will nominate CIA director Leon Panetta as defense secretary and Army General David Petraeus as head of the American spy agency, officials said on Wednesday.
Obama will also nominate veteran diplomat Ryan Crocker as the next U.S. ambassador to Afghanistan.
An official said Panetta's nomination would be announced later this week.
The positions would require Senate confirmation, suggesting the changes would not occur for some weeks or even months.
A shuffling of top national security jobs has been an object of speculation for weeks.
Robert Gates, the current Pentagon chief and a former CIA director, had made clear that he planned to step down as defense secretary this year.
Panetta, who turns 73 in June, is a long-standing Democratic Party figure who could prove closer to fellow Democrat Obama than Gates, who was appointed by former President George W. Bush and proved to be a maverick under both administrations.
Petraeus, 58, is a popular figure credited with pulling Iraq from the brink of civil war after the 2003 U.S. invasion before he assumed command of U.S. and NATO forces in Afghanistan.
Before word of the reshuffle broke, some Washington insiders suggested a Petraeus-for-Panetta swap could come as Obama gears up his 2012 re-election campaign.
They suggested the White House wanted a high-profile position for Petraeus to ensure he would not be tapped by Republicans to challenge Obama.