New Defense Secretary Ash Carter already is showing an independent streak, speaking out against the three-year timeline included in President Obama’s formal request for military force against the Islamic State.

Testifying before a House subcommittee on Wednesday, Carter called that timeline “political.”

“I wouldn't assure anyone that this will be over in three years or that the campaign will be completed in three years,” he said.

Carter was referring to the president’s recent congressional request for authorization of military force. That proposal would bar "enduring offensive ground combat operations" and let the authorization lapse after three years.

Doing so would put the debate to the next president over whether to renew the authorization – should it be approved.

While Carter raised concerns with the timeline, he also said he understands why it was included.

He said the three-year sunset “is not something that I would have deduced from the Department of Defense's necessities, the campaign's necessities, or our obligation to the troops.”

He added: “I think it has to do with the political calendar in our country. I understand that. That's a constitutional issue wherein the executive branch and the legislative branch share responsibility for the conduct of military operations.”

Carter recently took the helm of the Defense Department, replacing Chuck Hagel whose tenure was marked by disagreements with the Obama administration.

While Congress is weighing the request for military authorization, the president already has launched airstrikes and other military actions in Iraq and Syria. The White House nevertheless committed to putting the issue to a vote.

Asked Wednesday if he thinks additional U.S. troops will be needed in Iraq, or whether U.S. troops would be introduced in Syria, Carter left the door open.

“That is a question that will hinge upon what is required for success there,” he said.

Carter’s comments on Wednesday came after he also critiqued his own Central Command for a briefing given last month.

In that highly unusual briefing, an officer discussed a planned Iraqi-led offensive to retake Mosul from ISIS.

Carter, testifying Tuesday on the Senate side, said the information was inaccurate and should not have been provided regardless.

"That clearly was neither accurate information, nor had it been accurate would it have been information that should be blurted out to the press," Carter told the Senate Armed Services Committee. "So it's wrong on both ... scores."

Carter said it's important to be open, but "not with military secrets and not with war plans, which is the mistake here."