WASHINGTON: Brent Scowcroft, the respected national security advisor to two Republican presidents and a Washington heavyweight who served administrations from Richard Nixon to Barack Obama, has died aged 95, the George H.W. Bush Foundation announced Friday.

An outspoken critic of the US-led invasion of Iraq, Scowcroft was a member of the Republican foreign policy establishment who nevertheless endorsed Democrat Hillary Clinton during the 2016 presidential campaign. He died of natural causes, a statement from the foundation said. "No individual has provided as many commanders-in-chief as much national security advice - irrespective of party lines," the statement continued.