Macron said Europe had to think about its own security as the USA becomes a "less reliable" ally.
FILE - French President Emmanuel Macron pays his respects with children at the Ossuary of Douaumont near Verdun, northeastern France, Nov. 6, 2018, during ceremonies marking the centenary of the end of World War I.
President Trump on Friday lashed out at French President Emmanuel Macron - slamming him on Twitter for suggesting that Europe create its own military to protect it from Russia, China and the US.
"Very insulting", he added, "but perhaps Europe should first pay its fair share of North Atlantic Treaty Organisation, which the US subsidizes greatly!"
"Who is the main victim?"
The force, which would fall far short of an army in size and scope, would be able to rapidly mount a joint military operation, evacuate civilians from a war zone or provide aid after a natural disaster.
No sooner had Trump touched down in Paris for a weekend of commemorations to mark the end of World War 1, than he fired off a tweet castigating his host over proposals to endow the European Union with its own, joint army.
Sunday afternoon will see Mr Macron and Mrs Merkel attend a peace conference - the Paris Peace Forum - with leaders including Mr Putin and Turkey's Recep Tayyip Erdogan. Early on, Macron tried to position himself as a sort of "Trump whisperer" and Trump returned the favor, hosting Macron at the first and only state dinner of his presidency.
Trump is set to meet with Macron Saturday morning at the Élysée Palace in Paris, per USA Today.
The tone of this visit will be markedly less festive.
The president, joined by his wife Melania and high-ranking USA officials, arrived late on Friday aboard Air Force One for a visit that he called "very special" and one that he "looked forward to".
"I don't think we have anything scheduled in Paris and I'm coming back very quickly", the president said. At that meeting, Trump would not say whether he believed Putin or US intelligence agencies about their conclusions about Russia's interference with the 2016 presidential election.
Trump and Macron are schedule to have bilateral meeting during his stay in France.
The French president, who tried but failed earlier this year to talk Trump out of withdrawing from the 2015 Iran nuclear deal, has also voiced worries about the impact of sanctions on European companies doing business with Iran.