Chuck Hagel Monday resigned as US defence secretary after less than two years in the top military post, according to US media report.
Mr Hagel, 68, a Vietnam war veteran and former senator, became defence secretary in 2013.
Last month, it was reported that he was sharply critical of the US strategy against Islamic State and in relation to the Syria regime.
He is expected to stay on as secretary until his successor is confirmed.
An unnamed official told the Associated Press news agency that Mr Hagel and Mr Obama both "determined that it was time for new leadership in the Pentagon" and had been discussing the move for weeks.
The New York Times reported that Mr Obama had asked Mr Hagel to step down after the defence secretary opened up discussions of his leaving.
line
US Secretary of Defense Chuck Hagel speaks to members of 3rd Brigade, 4th Infantry Division, at the National Training Center in Fort Irwin, Calif. on 16 November 2014
Hagel's 58-41 confirmation was the narrowest ever vote margin for a Pentagon nominee
Analysis, Jon Sopel, North America Editor
Chuck Hagel is a friendly, no-nonsense defence secretary. He was also the one Republican in the White House national security set-up.
But that may be of lesser importance than him being appointed to do one task in the Pentagon, only to find that the job description has changed fundamentally.
He was the man appointed to bring the troops home and pare back the huge defence budget. But then Islamic State came along and all the calculations changed, and Mr Obama and his defence chief found themselves at odds.
There was a lack of clear strategy, perhaps because Mr Obama and Mr Hagel didn't agree on what it should be. And after mid-term political defeats, the president needs a military win. So a change at the top will be an important symbol of that determination.
Which of course leaves the question, did he jump or was he pushed? Probably a bit of both.
Mr Hagel, who served as Republican senator for his home state of Nebraska for 12 years, became critical of US involvement in Iraq despite voting to authorise the war.
He replaced Leon Panetta as defence secretary in Mr Obama's second term, taking on the task of winding down the Afghanistan war and making a military shift towards Asia.
But the future of US military policy has changed amid air strikes against IS in Iraq and Syria.
"The next couple of years will demand a different kind of focus," an unnamed White House official told the New York Times.
US media report there was increasing tension between Mr Hagel and the administration over decisions in Syria and working styles, citing Hagel confidantes and senior defence officials.
Mr Obama is not expected to announce a nominee to replace Mr Hagel on Monday. Once named, the nominee would have to be confirmed by the Senate.
Source:
http://www.ereporter.com.ng/index.php/world-news/item/1612-breaking-us-defence-secretary-chuck-hagel-resigns
Topic: BREAKING: US defence secretary Chuck Hagel Resigns (Read 844 times)
