US president Barack Obama revealed his choices to head the CIA and Pentagon on Monday, but the pair face a tough ride through Senate confirmation hearings.
Former Republican Chuck Hagel has been accused of being hostile towards Israel and soft on Iran - virtually sacrilege in the US.
CIA veteran John Brennan was linked to the agency's top job in 2008 but had to withdraw his name over links to the harsh interrogation techniques employed by the spying body.
Mr Brennan has denied involvement and strongly criticised the Bush-era pre-emptive invasions of foreign countries.