The request came from an official who said he had been briefed on requirements for the visit by the White House Military Office and the Seventh Fleet, which is stationed in Japan.

"USS John McCain needs to be out of sight," the email seen by the Wall Street Journal said. "Please confirm #3 will be satisfied," it added, referring to the request.

The order apparently posed a conundrum because the ship was undergoing repairs and would have been difficult to move before Trump arrived on Tuesday to deliver a speech on a neighboring ship.

In response, a tarpaulin was hung over the ship's name, which also refers to McCain's father and grandfather, the Journal said. The tarpaulin was removed before Trump arrived, but a barge was moved closer to the ship, blocking the view of its name.

Contacted by AFP, a spokesman for the Seventh Fleet said that photos showing a tarp over the name of the ship were from Friday and that the barge was moved out of the way on Saturday, days before Trump's visit.

"All ships remained in normal configuration during the President's visit," Commander Clay Doss said.

The New York Times however cited two Navy sailors as saying sailors from the McCain were not invited to hear Trump speak, unlike those serving on other US warships at the base.

And when several showed up anyway, wearing uniforms bearing the name of the ship, they were turned away, the newspaper reported.

The Journal said acting Defense Secretary Patrick Shanahan was aware of the concern about the ship's name and "approved measures to ensure it didn't interfere with the president's visit."

- Trump denies involvement -

But Shanahan, speaking during a visit to Jakarta as part of a regional tour, denied any prior knowledge.

"When I read about it this morning, it was the first I heard about it," he told reporters.

"I need to find out a little bit more," he added, when asked if he planned an investigation.

Trump too denied any knowledge of a directive to cover up the name.

"I was not informed about anything having to do with the Navy Ship USS John S. McCain during my recent visit to Japan," the president tweeted.

"Nevertheless, @FLOTUS and I loved being with our great Military Men and Women - what a spectacular job they do!"

Trump had a combative political relationship with McCain, who died in August and was taken prisoner and tortured during the Vietnam war.

Despite never serving in the military himself, Trump mocked the moderate Republican's war hero status in 2015.

McCain, a respected figure in US politics for decades who himself ran for president twice, withdrew his support for Trump in the 2016 presidential election and blocked Trump's healthcare efforts in Congress in 2017.

And before the senator died of brain cancer at the age of 81, he said he didn't want Trump attending his funeral.

Even after McCain's death, the president has continued to make his dislike clear: "I was never a fan of John McCain and I never will be," Trump said in March.

"Trump is a child who will always be deeply threatened by the greatness of my dads incredible life," McCain's daughter Meghan tweeted Wednesday evening after the reports emerged.

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