The rationale behind the idea of creating a European army, which has been floated repeatedly through the years but has yet to materialize, is to lessen Europe's dependence on the whims of the U.S. politicians, Macron indicated.
Trump's talks with Macron at Elysee Palace are likely to cover European concerns about Trump's plans to withdraw the United States from the 1980s Intermediate-Range Nuclear Forces Agreement and USA renewal of sanctions against Iran.
He's expected to meet with leader Emmanuel Macron Saturday, to discuss a range of issues including trade.
In the touchdown tweet, Trump suggested Europe first pay "its fair share" of North Atlantic Treaty Organisation before contemplating a Europe-wide force.
"We have to protect ourselves with respect to China, Russia and even the United States", he told France's Europe 1 radio.
Both Mr Trump and Mr Putin will be among the leaders attending that ceremony. Trump said on Wednesday that he will have lunch with Russian President Vladimir Putin among other leaders during his planned trip to Paris but no meeting was expected.
Trump, who is visiting France with his wife Melania for the second time since becoming president, was referring to a call made by Macron in an interview Tuesday for a "real European army". Europe, he said in Tuesday's Europe 1 radio interview, must reduce its dependence on US after Trump announced he was pulling out of a Cold War-era nuclear treaty.
The president, joined by his wife Melania and high-ranking United States officials, arrived late on Friday aboard Air Force One for a visit that he called "very special" and one that he "looked forward to". That now seems more likely for later this month, when they attend the Group of 20 summit of global leaders in Argentina. "Europe and its security", he said.
He has railed against trade deals with the European Union and has criticised some EU nations, including France, for not spending enough on defence to sustain North Atlantic Treaty Organisation, the decades-old Western alliance formed as a bulwark to Moscow's aggression. Early on, Macron tried to position himself as a sort of "Trump whisperer" and Mr. Trump returned the favor, hosting Macron at the first and only state dinner of his presidency.
The White House and the Kremlin had previously considered a formal meeting in Paris.
Trump launched a broadside at Macron via his preferred medium of conducting foreign policy - Twitter.
The president told reporters Wednesday that he would not be holding an extended meeting Putin before the G-20 summit later this month in South America, though said he won't be surprised if the two interact during the leaders' luncheon at the Elysee Palace on Sunday.