Trump arrived in the French capital after an overnight flight from Washington and hours before his meeting with Macron to tackle potential solutions to the crisis in Syria and broader counterterrorism strategies.
Trump's decision last month to withdraw the U.S. From the Paris climate accord sparked outrage across Europe and anti- Trump protests are planned while he is in Paris.
Macron, a staunch advocate of research to combat global warming, has beckoned "all responsible citizens," including American scientists and researchers, to bring their fight against climate change to France.
Trump came to his son's defense Wednesday, praising Donald Trump Jr.'s performance in an interview on Fox News Channel. Trump tweeted: "He was open, transparent and innocent. This is the greatest Witch Hunt in political history. Sad!"
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The visit to Paris could offer Trump a well-timed distraction from the controversy. He will mark the 100th anniversary of America's entry into World War I by visiting US troops. He'll also be the guest of honor at Friday's Bastille Day events - a celebration of French national pride.
The leaders and their wives will end a busy day of meetings Thursday with a lavish dinner at Jules Verne at the top of the Eiffel Tower.
Trump is visiting a city he has repeatedly disparaged. When he announced his decision on the climate agreement, Trump said he was "elected to represent the citizens of Pittsburgh, not Paris." And he's repeatedly said the city has been ruined by the threat of terrorism, which he ties to immigrants.
"Paris isn't Paris any longer," he said in February. But counterterrorism issues give Macron and Trump the potential for a strong working relationship.
France has been plagued in recent years by extremist attacks. During last year's Bastille Day celebrations, a 19- ton cargo truck deliberately plowed into crowds in Nice, killing more than 80 people.