US President Donald Trump has gone on Twitter to mock his French counterpart, Emmanuel Macron, after an awkward Armistice Day visit.
He attacked Mr Macron over nationalism, plans for a European army, French tariffs on US wine imports, and the French leader's popularity rating.
Mr Macron had urged world leaders to reject nationalism, describing it as a "betrayal of patriotism".
Some observers interpreted the remarks as a thinly-veiled attack on Mr Trump.
"By saying 'our interests first and never mind the others' you stamp out the most precious thing a nation has - its moral values," Mr Macron said, in a speech to mark the 100th anniversary of the Armistice that ended World War One.
Mr Trump's relations with European and fellow Nato leaders have long been strained.
German Chancellor Angela Merkel came to Mr Macron's defence on Tuesday, echoing his call for a "real European army".
What's eating Trump?
By Hugh Schofield, BBC News, Paris
As the French might well ask: quelle mouche a piqué Donald Trump? What fly has bitten the US president? Why is he suddenly on an anti-France tirade?
The answer - presumably - is that he resents being the butt of Emmanuel Macron's speechifying. The French leader went on one of his rhetorical flights at Sunday's armistice ceremony, and his main target (aka Potus) was sitting right in front of him.
Macron sought in his address to draw a distinction between patriotism (good) and nationalism (bad). Patriotism was what inspired the self-sacrifice of the First World War. Nationalism, he implied, is what inspires Donald Trump.
Trump disputes this as a false dichotomy. He thinks nationalism and patriotism are essentially the same, and in his tweet he turns the tables on Macron by saying that the French as a people are actually nationalist, and should be proud of it.
Words mean what we choose them to mean. Patriotism is for Macron a good word because in his mind patriots fight for values, not for "my country right or wrong". Trump, presumably, thinks that is pious hogwash.
What exactly did Macron and Trump say about nationalism?
Speaking at the Arc de Triomphe in Paris on 11 November, Mr Macron called on fellow leaders to "fight for peace", saying: "Ruining this hope with a fascination for withdrawal, violence or domination would be a mistake for which future generations would rightly find us responsible."
He called nationalism "a betrayal of patriotism".
Far from frowning on nationalism, the US president appeared on Tuesday to hold France up as an example for nationalists to emulate.
The problem is that Emmanuel suffers from a very low Approval Rating in France, 26%, and an unemployment rate of almost 10%. He 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!........— Donald J. Trump (@realDonaldTrump) November 13, 2018
......MAKE FRANCE GREAT AGAIN!— Donald J. Trump (@realDonaldTrump) November 13, 2018
When Mr Trump attacked his French counterpart's falling personal approval rating - which one poll put as low as 21%- he was safe in the knowledge that his own rating was above 40% just before the US mid-term elections last week.
How about France's military record?
Talking about cyber threats in a radio interview, he referred to protecting France "with respect to China, Russia and even the United States of America".
Reconciliation between France and Germany was a major theme of the World War One Armistice commemorations
Addressing the European Parliament in Strasbourg on Tuesday, Mrs Merkel said: "We should work on a vision of one day establishing a real European army."
She insisted this would not be an army against Nato but rather a good - and streamlined - supplement to it.
Her decision to throw her weight behind Emmanuel Macron's vision for a European military is likely to enrage Donald Trump, BBC Berlin correspondent Jenny Hill reports.
On Twitter, Mr Trump launched a gibe at France's defeat and occupation by Nazi Germany in World War Two.
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? They were starting to learn German in Paris before the U.S. came along. Pay for NATO or not!— Donald J. Trump (@realDonaldTrump) November 13, 2018
And the wine?
The US leader accused France of making it hard for America to sell its wine there.
On Trade, France makes excellent wine, but so does the U.S. The problem is that France makes it very hard for the U.S. to sell its wines into France, and charges big Tariffs, whereas the U.S. makes it easy for French wines, and charges very small Tariffs. Not fair, must change!— Donald J. Trump (@realDonaldTrump) November 13, 2018
An unnamed source in the French presidential palace has told media that it does not comment on tweets clearly aimed at Mr Trump's domestic audience.
"Trump's tweets are intended for Americans," the source said. "Otherwise they wouldn't be written in English. We have no comment on content that is intended for his own citizens."
Relations between Mr Trump and Mr Macron have not always been so poor. At one stage there was even talk of an unlikely "bromance" between them.
What about not going to the cemetery?
Mr Trump has been widely criticised on Twitter for failing to visit a US war cemetery at Belleau near Paris on Saturday because of rain.
One British MP, Sir Nicholas Soames, who is a grandson of wartime leader Sir Winston Churchill, said he was unfit to be president.
On Tuesday, Mr Trump tweeted his reasons and pointed out that he had attended Sunday's events despite the rain then too.
By the way, when the helicopter couldn’t fly to the first cemetery in France because of almost zero visibility, I suggested driving. Secret Service said NO, too far from airport & big Paris shutdown. Speech next day at American Cemetery in pouring rain! Little reported-Fake News!— Donald J. Trump (@realDonaldTrump) November 13, 2018