SEOUL, South Korea — The Pentagon has told the White House to stop politicizing the military, amid a furor over a Trump administration order to have the Navy ship named for the late Sen. John McCain hidden from view during a presidential visit.

A defense official said Acting Defense Secretary Patrick Shanahan is also considering sending out formal guidance to military units in order to avoid similar problems in the future.

Shanahan, who was traveling to South Korea on Sunday, confirmed details about a Navy email that said the White House military office wanted the USS John McCain kept “out of sight” when President Donald Trump visited Japan about a week ago. The internal Navy email came to light last week, triggering a storm of outrage.

Trump, who long feuded with McCain, has said he knew nothing about the request, but added that "somebody did it because they thought I didn't like him, OK? And they were well-meaning, I will say."

Shanahan told reporters traveling with him to Seoul that he is not planning to seek an investigation by the inspector general into the matter, "because there was nothing carried out" by the Navy. He added that he still needs to gather more information about exactly what happened and what service members did.

"How did the people receiving the information — how did they treat it," Shanahan said. "That would give me an understanding on the next steps" to take.

Shanahan did not detail what the next steps could be, but a defense official said Shanahan is considering a clearer directive to the military about avoiding political situations. The goal would be to ensure there is less ambiguity about how the military should support VIP events and how service members should respond to such political requests, said the official, who spoke on condition of anonymity to discuss internal deliberations.

Shanahan also said that he spoke with McCain's wife, Cindy, about the incident a couple days ago, but he declined to provide any details.

The order to keep the Navy destroyer out of sight reflected what appeared to be an extraordinary White House effort to avoid offending an unpredictable president known for holding a grudge, including a particularly bitter one against McCain.

The McCain incident has dogged Shanahan throughout his weeklong trip to Asia, even as he tried to deal with critical national security issues involving the eroding U.S. relationship with China and the continuing threat from North Korea.

Shanahan, who has been serving in an acting capacity since the first of the year, has yet to be formally nominated by Trump as permanent defense chief. His speech to a major national security conference in Singapore on Saturday was a chance to audition for the job on the international stage.

A formal nomination has been expected, and Congress members have said they believe there will be a hearing on his nomination in the next month or so.

According to Shanahan spokesman Lt. Col. Joseph Buccino, Shanahan told his chief of staff on Friday to speak with the White House military office "and reaffirm his mandate that the department of defense will not be politicized." Buccino said the chief of staff reported back that he delivered the message.

Asked what he has gleaned about the incident so far, Shanahan said he was told that despite the White House request, the Navy did not move the ship and that a barge that was in front of it was moved before Trump arrived. He said that a tarp that had been draped over the ship's name was removed, but that it was put there for maintenance, not to obscure its identity.

Asked directly if his senior staff was aware of the White House request before the president’s visit, Shanahan said he’s been told they did not know. He also has said he was not aware of the request and that he would never have authorized it.