WASHINGTON — President-elect Obama has hired veteran Democrats Sam Nunn and Warren Christopher to head his transition teams at the Pentagon and State Department, senior government officials and others said yesterday.

Nunn is a former Georgia senator who was chairman of the Senate Armed Services Committee. Christopher was President Clinton's first secretary of state. They are part of a national security brain trust for Obama that is heavy on former Clinton administration officials, including possible national security adviser James Steinberg, a former State Department official.

Obama's national security transition offices will work with the Bush administration to hand off management of two wars and complex diplomacy with North Korea, Russia and other nations. Obama has not announced his choices for secretaries of state and defense.