Chuck Hagel Resigns As US Defence Secretary

Defence Secretary Chuck Hagel has stepped down amid criticism of the campaigns in Afghanistan and against the Islamic State.

Barack Obama said the 68-year-old former senator and Vietnam war veteran approached him last month about resigning.

Mr Hagel told the President it was an "appropriate time to complete his service", Mr Obama said during a warm send off at the White House on Monday.

"Over nearly two years, Chuck has been an exemplary Secretary of Defence," the President said.

He thanked Mr Hagel for "always giving it to me straight".

Hagel, a former Republican senator, has agreed to stay on until the Senate approves a successor.

Mr Hagel took on the role of Pentagon chief in early 2013 following a tense Senate approval process.

Speaking at the White House on Monday, Mr Hagel said he was "immensely proud" of what was accomplished during his tenure.

Mr Hagel served as senator from Nebraska and became a critic of US involvement in Iraq. He received two Purple Hearts for his service in the Vietnam War.

Sky News US correspondent Dominic Waghorn said: "He has had outstanding differences with the close-knit team of advisors around the President, he's never quite managed to break into that.

"And over the last few weeks and months there have been real points of disagreement between him and other officials in the Pentagon… on the issue of ISIS, on the issue of what to do in Syria in particular."

Speculation had mounted in recent weeks over Mr Hagel's future in the administration, and he himself addressed those rumours during an interview with Charlie Rose last week.

"I don't get up in the morning and worry about my job," he said.

"It's not unusual by the way, to change teams at different times."

Top potential candidates to replace Mr Hagel include Michele Flournoy, a former under-secretary of defence, and Ashton Carter, a former deputy secretary of defence.

Both were considered contenders for the job before Mr Hagel was named at the start of Mr Obama's second term.

Senator Jack Reed, Democrat of Rhode Island, is another possible contender.