Hagel resigns as US defence secretary

WASHINGTON, Nov 25 (Reuters):  US Defence Secretary Chuck Hagel resigned on Monday, leaving under pressure as President Barack Obama faces critical national security challenges, including fighting Islamic State in Iraq and Syria and revising plans to exit Afghanistan.

It was the first major change to Obama's Cabinet since his Democrats were routed in midterm elections three weeks ago, and Republicans, who now control both houses of Congress, are looking for a new approach from the White house.

Hagel was appointed less than two years ago as Obama pushed his signature program of winding down wars in Afghanistan and Iraq, a process now being upended with U.S. re-engagement in Iraq and greater military cooperation with Kabul.

He had privately expressed frustration to colleagues at the administration's strategy toward Iraq and Syria and at his lack of influence over the decision-making process, a source familiar with the situation said.