WASHINGTON — After outlining a new defense strategy marked by a smaller, leaner military, President Barack Obama on Thursday could not resist a less serious postscript about his surroundings.

“I understand this is the first time a president’s done this,” he told reporters, glancing up at Pentagon briefing room 2E973. “It’s a pretty nice room.”

Obama’s remarks highlighted the rareness of a sitting president holding a news briefing at the Pentagon’s go-to meeting place, typically reserved for defense officials flanked by uniformed military leaders. The president’s comments also demonstrated his similarly uncharacteristic closeness to the development of the new defense policy, a point Defense Secretary Leon Panetta made early in his own speech.

“In my experience, this has been an unprecedented process — to have the president of the United States participate in discussions involving the development of a defense strategy, and to spend time with our service chiefs and spend time with our combatant commanders to get their views,” Panetta said Thursday after the president’s 10-minute address.

A defense department spokeswoman said that Obama was indeed the first president to deliver a press briefing from the Pentagon.

On Thursday morning, the president was joined by the room’s usual cast, including Panetta and Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, both of whom clarified the strategy’s finer details to reporters after the president spoke. But news cameras fell squarely on Obama as he entered the briefing room shortly after 11 a.m. in what many media outlets described as an out-of-the-ordinary appearance for the commander in chief.

In addition to citing his own involvement in the defense budget deliberations, Obama’s trip across the Potomac to the Pentagon signaled unity between his administration and the defense leadership, said Martha Joynt Kumar, a professor of political science at Towson University. She specializes in White House communications and, according to her website, “managing the president’s message.”

“He wants to show that everybody’s together behind cuts to the military,” Kumar said. “A very good way to send that message is to send that message visually. Get everybody together. And that’s what he did.”

Leroy D. Dorsey, the chair of the communication department at the University of Memphis, agreed such atypical presidential appearances are intended to bring  a certain cause into the public view.

Dorsey said the setting for a presidential speech often means just as much as the  words themselves.

“Presidents are purposeful agents,” Dorsey said. “Everything they do is designed to perpetuate a message, or a position, or a point of view. So the fact that he’s giving a speech in a place a president doesn’t normally give a speech is meaningful in and of itself.”

Dorsey added although he did not watch Thursday’s news conference, “just given that he [Obama] gave it where he gave it, he wants to draw more attention to it.”

In a letter attached to the new defense plan, Obama emphasized the urgency  of moving forward with the military outline. The nation is “at a moment of transition” and requires a critical reevaluation of its armed forces, the president wrote.

He was even more emphatic during his remarks at the Pentagon.

“We need to be smart, strategic and set priorities,” Obama said. “The new guidance that the Defense Department is releasing today does that.”

The defense strategy accommodates $487 billion in cuts to military spending over the next decade, Panetta said. Speakers at the news conference agreed that fiscal situation calls for a smaller, leaner defense budget and adjusted military presences in the Asia-Pacific region and the Middle East.

Obama had a more casual message for reporters gathered in the briefing room. Although he did not take questions, the president briefly turned to his audience after shaking hands with defense leaders.

“Take it easy on ’em,” Obama told reporters, pointing to the gaggle of military officials left behind as he excused himself from their home field.