WASHINGTON — Mick Mulvaney, President Trump’s acting chief of staff, sought on Sunday to play down the White House’s directive to hide a Navy destroyer named after Senator John McCain during the president’s visit to a naval base in Japan last week.

Mr. Mulvaney said that a young White House staff member, knowing of Mr. Trump’s animosity toward Mr. McCain, most likely made the request to the Navy to block the warship from view. The Navy at first complied, placing a giant tarp over the name and then hiding it with a barge before senior admirals reversed the decision.

“If a 23- or 24-year-old person says, ‘Look, is it really a good idea for this ship to be in the background?’ that is not an unreasonable question,” Mr. Mulvaney said on “Fox News Sunday,” adding, “We think it’s much ado about nothing.”

Asked about the matter on NBC News’s “Meet the Press,” Mr. Mulvaney said it would be “silly” to fire the aide over the episode, which has drawn a torrent of criticism from retired military officers.