Donald Trump on Tuesday unleashed an extraordinary attack on Emmanuel Macron, mocking the French president's approval rating and lashing him over European defense proposals which enjoyed a crucial new boost from Germany.

On the heels of a rocky trip to Paris to mark the World War I centenary, Trump fired off a caustic series of early-morning tweets against his weekend host and renewed his frequent charge that America's European allies in NATO spend too little on defense.

"Emmanuel Macron suggests building its own army to protect Europe against the U.S., China and Russia. But it was Germany in World Wars One & Two - How did that work out for France?" Trump tweeted.

"They were starting to learn German in Paris before the U.S. came along," he added, in a low blow sure to gall many French. "Pay for NATO or not!"

"MAKE FRANCE GREAT AGAIN!" Trump continued in a play on his own campaign slogan, before turning to what he slammed as protectionist French tariffs on US wine -- saying they were "not fair, must change!"

The fierce broadside comes as Europeans increasingly ask whether they should rely on the mercurial Trump and the United States for defense, which has been assured during the Cold War and beyond by the NATO alliance stretching from Alaska to Turkey.

German Chancelor Angela Merkel -- who, unlike Macron, has barely concealed her disdain for Trump -- on Tuesday voiced clear support for France's idea of a common European defense.

"What is really important, if we look at the developments of the past year, is that we have to work on a vision of one day creating a real, true European army," Merkel told a session of the European Parliament, drawing applause and some boos.

Merkel said that the European army would function in parallel to NATO and come under a European Security Council, which would centralize defense and security policy on the continent.

"Europe must take our fate into our own hands if we want to protect our community," said Merkel, a day after her show of unity with former enemy France on the anniversary of the end of the Great War.

- Rebukes on both sides -

Trump had already berated Macron in a tweet from Air Force One just as he landed in Paris, calling the French proposals for European defense "very insulting."

Trump appeared to be incensed after critical media coverage of his trip -- during which he was called out for canceling a visit to an American military cemetery after his helicopter was grounded by the rain.

Adding to the rough reception, Macron in his Armistice Day speech declared that nationalism "is a betrayal of patriotism," in a clear rebuke of the self-described nationalist Trump, who was in attendance.

"By saying our interests come first and others don't matter we are erasing what makes a nation precious, what makes it live, what makes it great and most importantly of all, its moral values," Macron said.

Trump, referring to the push for a European military, tweeted that Macron was "just trying to get onto another subject."

"By the way, there is no country more Nationalist than France, very proud people-and rightfully so!" Trump said.

Macron's office offered no comment on Trump's criticism. But an adviser to Macron, who declined to be named, brushed aside the tweets, saying they were "written for Americans -- otherwise they would not be written in English."

Gilbert Collard, an MP from France's far-right National Front, applauded Trump's attack on Macron -- but not on French wine.

"I want to tell Donald -- drink your Coke, do your tweets and leave it to us to make good wine," he said.

- 'Bromance' dead? -

Trump and Macron had seemed to share a special camaraderie in the early days of their respective presidencies, a "bromance" of sorts that included touching, kissing and playful banter.

The US president even seemed to flick a piece of dandruff off of Macron's jacket on national television during the French president's state visit to the US capital, saying "we have to make him perfect. He is perfect."

But the relationship took a turn for the worse over the European defense calls by Macron, who cited the United States along with Russia and China as threats to European cybersecurity.

In an interview recorded Saturday with CNN after talks with Trump, Macron described the spat as a misunderstanding, with both sides in agreement that Europe should spend more on defense.

But Macron said: "To be very direct with you, what I don't want to see is European countries increasing the budget in defense in order to buy American and other arms or materials coming from your industry."

Trump in his tweets also defended the cancelation of the cemetery trip, saying that the Secret Service rejected his suggestion to drive instead of take a helicopter.

He pointed out that he had delivered a speech the following day at another American cemetery in the Paris suburbs "in pouring rain!"

"Little reported-Fake News!" he charged.