US President Barack Obama has nominated Republican Chuck Hagel as his next defence secretary and White House counterterrorism adviser John Brennan as the new CIA director.

Mr Hagel, a maverick former Republican senator and decorated Vietnam veteran, had been widely tipped to replace Leon Panetta at the Pentagon.

The move will likely set up a tough Senate confirmation battle against critics who have attacked his record on Israel and Iran.

Mr Brennan, who formerly served at the CIA, will succeed retired general David Petraeus, who resigned amid a scandal over an extramarital affair with his biographer.

The addition of Mr Hagel and Mr Brennan follows Senator John Kerry's nomination for secretary of state.

Mr Obama will rely on them as he faces daunting challenges of winding down the war in Afghanistan, dealing with the Iranian nuclear standoff and curbing Pentagon spending.