PARIS – Hours before embarking on a ceremony to honor the 75th anniversary of the D-Day invasion, President Donald Trump reopened a squabble with a member of the British royal family, slammed a Democratic presidential candidate on Twitter and downplayed protests over his European visit.

In a prominent interview that aired Wednesday morning in the U.K. and a series of subsequent tweets, Trump blasted former Vice President Joe Biden for reports that his campaign appeared to plagiarize passages of its newly released climate policy and then sought to re-litigate a fight with Meghan Markle, whom he described in a recent interview as "nasty."

The president, who is meeting with European leaders this week and attending ceremonies to honor the 75th anniversary of the D-Day invasion in Normandy, has simultaneously battled with the Duchess of Sussex, the mayor of London and others in the run up to ceremonies that will begin Wednesday on the south coast of Britain.

“She was nasty about me,” Trump said in an interview with Piers Morgan that aired Wednesday morning in Britain. “That's OK for her to be nasty. It's not good for me to be nasty to her and I wasn't."

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Trump was referring to an interview in Washington last Friday with The Sun, in which reporters asked for Trump's thoughts on the former American actress, who "wasn’t so nice" to him during the 2016 U.S. presidential election.

"I didn’t know that. What can I say? I didn’t know that she was nasty," Trump said.

Trump, who often makes waves during his overseas visits and who began this week-long trip with a Twitter fight aimed at London Mayor Sadiq Khan, also said he met with Prince Harry, despite rumors that Harry had avoided an exchange.

“I congratulated him. I think he's terrific – he couldn't have been nicer,” Trump said.

Trump's Twitter feed initially focused on the pomp surrounding his formal state visit with Queen Elizabeth II, but days later the president bashed actor and singer Bette Midler, a frequent sparring partner, describing her in a tweet as a "sick scammer."

Then, hours later, he blasted Biden, weighing into the 2020 race while overseas. Some Republicans criticized Trump days ago for criticizing Biden while visiting Japan.

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"Plagiarism charge against Sleepy Joe Biden on his ridiculous Climate Change Plan is a big problem, but the Corrupt Media will save him," Trump tweeted.

In his television interview,Trump also appeared to walk back an assertion he made hours earlier during a press conference with outgoing British Prime Minister Theresa May. At the press conference, Trump said that Britain’s National Health Service could be part of a negotiation for a new trade deal between the U.S. and the U.K.

Some Britons fear the trade talks could open up the country’s health care system to private U.S. firms.

But after an uproar over his comments, Trump appeared to reverse course.

“That's something I would not consider part of trade,” he told Morgan. “That's not trade.”