Outgoing Defense Secretary Chuck Hagel, in a statement to Pentagon staff, says he made the decision to resign “after much discussion” with President Obama. 

Allegations have surfaced from anonymous defense officials that Hagel, the lone Republican on Obama’s national security team and the first enlisted combat veteran to serve as Pentagon chief, was forced to step down under pressure from the White House. 

“He wasn’t up to the job,” one senior defense official told NBC News

Citing another anonymous defense official, NBC News reports that the White House lost confidence in Hagel. 

“You should know I did not make this decision lightly. But after much discussion, the President and I agreed that now was the right time for new leadership here at the Pentagon,” said Hagel in the statement issued shortly after President Obama announced that he had accepted the defense secretary’s resignation.

“I want you to know that I am immensely proud of what we have accomplished together. We have prepared ourselves, our Allies and the Afghan National Security Forces for a successful transition in Afghanistan. We have taken the fight to ISIL and, with our Iraqi and coalition partners, have blunted the momentum of this barbaric enemy,” added the defense secretary. 

“We have bolstered enduring alliances and strengthened emerging partnerships, all the while setting in motion important reforms that will prepare this institution for the challenges facing us in the decades to come,” later said Hagel. “Most importantly, we have helped keep this country and our fellow citizens safe. We have sustained the blessings of liberty our ancestors secured and upheld the oath we took.” 

President Obama praised Hagel’s service in announcing his resignation, which was first reported by The New York Times

John McCain (R-Ariz.), expected to be the incoming chairman of the Senate Armed Services Committee, indicated that Hagel was “frustrated” with the Obama administration. 

“I know that Chuck was frustrated with aspects of the Administration’s national security policy and decision-making process,” said McCain in a statement responding to Hagel stepping down. “His predecessors have spoken about the excessive micro-management they faced from the White House and how that made it more difficult to do their jobs successfully. Chuck’s situation was no different.” 

“I hope the President will nominate a secretary of defense with the strength of character, judgment, and independence that Bob Gates, Leon Panetta, and Chuck Hagel all exhibited at their best,” he added. “But ultimately, the President needs to realize that the real source of his current failures on national security more often lie with his Administration’s misguided policies and the role played by his White House in devising and implementing them. That is the real change we need right now.”

According to the Times, the following are on the top of the list to replace Hagel: 

Michèle Flournoy, a former under secretary of defense; Sen. Jack Reed (D-R.I.), a former officer with the Army’s 82nd Airborne; and Ashton B. Carter, a former deputy secretary of defense.

A spokesman for Reed, in a statement, said the senator is not interested in becoming the next secretary of defense, NBC News reported.

Hagel said he will wait for the Senate to confirm his replacement before resigning his defense secretary post.