Hagel, under pressure, resigns as U.S. defence secretary

U.S. President Barack Obama (R) announces the resignation of Defense Secretary Chuck Hagel (L) at the White House in Washington, November 24, 2014. REUTERS/Larry Downing

WASHINGTON (Reuters) - U.S. Defense 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.