U.S. Defense Secretary Hagel Resigns as IS War Heats Up

President Barack Obama announced the departure of U.S. Defense Secretary Chuck Hagel on Monday, with the White House under fire over perceived fumbling in its response to the Islamic State threat.

The former Republican senator, who has been in the job for less than two years, was chosen to oversee a shift to a peacetime military with smaller defense budgets, but found the United States at war again.

Rapid advances by Islamic State jihadists in Syria and Iraq forced the Pentagon chief into managing a complex campaign, and Obama concluded Hagel was not the man for the task.

The 68-year-old Vietnam war veteran joined Obama at the White House to confirm his departure.

"When I asked Chuck to serve as secretary of defense we were entering a significant period of transition: the drawdown in Afghanistan, the need to prepare our forces for future missions and tough fiscal choices to keep our military strong and ready," Obama said.

"Last month, Chuck came to me to discuss the final quarter of my presidency and determined that, having guided the department through this transition, it was an appropriate time for him to complete his service."

Both Obama and Hagel presented the decision as mutually agreed, but administration officials privately suggested he had been pushed out, while Obama's critics said Hagel had become frustrated.

At the White House announcement, Hagel thanked Obama for his "friendship" and "leadership," saying he believed he had put the military and the nation on a "stronger course toward stability."

On jihadist websites and Twitter accounts, Islamic State supporters celebrated "victory" against Hagel, claiming he had been forced out by their successes against U.S. allies on the battlefield.

The White House did not say who might be Hagel's eventual replacement at the Pentagon, but in Washington three candidates are widely considered to be in the running.

Former under-secretary of defense Michele Flournoy, who would be the first woman to run the Pentagon, is touted as the most likely choice, followed by former deputy secretary Ashton Carter. 

Senator Jack Reed of Rhode Island -- a former army airborne officer -- has also been cited as a plausible contender, but his spokesman told reporters that he was not interested in the job.

Confirmation hearings for whoever gets the nomination will provide Republican critics a platform to slam the Obama administration's campaign against the Islamic State group.

Some hawks are demanding bolder action, including the use of U.S. ground units to help Iraqi and Kurdish forces in their battle to contain the jihadist threat.

As a senator, Hagel voted in favor of the 2003 U.S. invasion of Iraq, but later became a critic of the drawn-out conflict that ensued.

Hagel's combat experience as a non-commissioned officer who was wounded in Vietnam was seen as a strength as he took on the job.

But his public appearances have often appeared clumsy or underwhelming as the administration struggles to adapt to new conflicts and articulate its strategies. 

Although administration officials indicated the defense secretary had been pressured to resign, a senior national security staff member in Congress told Agence France-Presse that was not the case.

"Hagel quit," the aide said. "Hagel found himself at odds with the administration."

Hagel's experience was similar to that of his predecessors, Robert Gates and Leon Panetta, who both complained after they left office of meddling by political appointees in the White House, the aide and some lawmakers said.

Senator John McCain, an outspoken critic of Obama's foreign policy, said he had spoken to Hagel by phone Monday. 

"I know that he was very, very frustrated," McCain said.

"Already the White House are leaking, 'Well he wasn't up to the job.' Believe me, he was up to the job."

McCain said the Obama administration had "no strategy" to fight the Islamic State group and that Hagel had never been allowed into a White House inner circle making decisions.

Hagel had disagreed with the administration's approach to Syria, writing a two-page memo arguing for a more assertive stance towards President Bashar Assad, his aides recently disclosed.

Apart from the air war against the IS group, the White House has also come under criticism for its plans in Afghanistan, with some Republicans questioning a timeline that will have all U.S. troops out of the country by the end of Obama's term in two years.

Speculation about Hagel's future gathered steam in October, when anonymous administration officials criticized his performance to a high-profile Washington Post columnist, David Ignatius.

Hagel was once considered a potential Republican presidential contender but in his current job, officials said he often said little at strategy sessions in the White House situation room.

Earlier this month, Hagel called off a long-planned trip to Vietnam and Myanmar at the last moment.