Dick Cheney, a driving force behind the US invasion of Iraq in 2003 who was considered by presidential historians as one of the most powerful vice-presidents in US history, has died at age 84.

Cheney died on Monday night from complications of pneumonia and cardiac and vascular disease, his family said.

The Republican - a former Wyoming congressman and secretary of defence - was already a major Washington player when then-Texas governor George W Bush chose him to be his running mate in the 2000 presidential race that Bush went on to win.

As vice-president from 2001 to 2009, Cheney fought vigorously for an expansion of the power of the presidency, having felt that it had been eroding since the Watergate scandal that drove his one-time boss Richard Nixon from office.

He also expanded the

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