Obama: Defense nominee Ashton Carter will hit the ground running

President Obama nominated former Pentagon official Ashton Carter Friday to become his fourth Defense secretary in less than six years, an event that departing Defense Secretary Chuck Hagel pointedly skipped.

“Ash is rightly regarded as one of our nation’s foremost national-security leaders,” Mr. Obama said at the White House. “He’s played a key role in devising our defense strategy.”

Mr. Carter said he accepted the nomination in part due to his “high regard” for Mr. Obama’s leadership.

“If confirmed in this job, I pledge to you my most candid strategic advice,” Mr. Carter told the president. “And I pledge also that you will receive equally candid military advice.”

The White House had said Mr. Hagel would attend the event, but he was a no-show at the announcement. A Defense Department official said Mr. Hagel “believes strongly that this day belongs to Ash Carter and his nomination to be the next secretary of Defense.”

“As Secretary Hagel knows better than most, today is a day that is to celebrate Ash, his family, and all that he will accomplish,” the official said on background. “The secretary is proud of Ash and of their friendship and does not want in any way to detract from or distract the proper focus of the day.”

Mr. Hagel said Thursday that his resignation was not prompted by “major differences” with Mr. Obama, rebutting reports that he had been fired or quit due to White House micromanagement. He said he decided to step down after several conversations with the president led him to believe that the Pentagon needed a change in leadership.

White House press secretary Josh Earnest said the president didn’t consider Mr. Hagel’s absence a snub.

“Certainly it was a decision that was respected by everybody here at the White House,” he said.

In Mr. Hagel’s absence, the president quoted him from a year ago, when Mr. Hagel spoke at the occasion of Mr. Carter leaving his previous Pentagon job.

“Chuck then went on to express his gratitude to his partner for ’what Ash has done for this country and will continue to do in many ways,’” Mr. Obama said. “Couldn’t have said it better myself.”

The president said Mr. Carter will be crucial in forging a “leaner” military over the next two years.

“He’s a reformer who’s never been afraid to cancel old or inefficient weapons programs,” Mr. Obama said. “He knows the Defense Department inside and out.”

Mr. Carter served as deputy Defense secretary from October 2011 to December 2013, when he was the Pentagon’s chief operating officer. For two years prior to that, he served as the Defense Department’s chief weapons buyer.

Senators of both parties have said they expect Mr. Carter, who’s been confirmed three times by the Senate, to have a relatively smooth confirmation.