Donald Trump has appeared to endorse far-Right leader Marine Le Pen days before the French election following the murder of a policeman in a terrorist attack in Paris.
The US president tweeted early on Friday morning that "France will not take much more of this".
He added: "Will have a big effect on the presidential election" - seeming to suggest that it will push voters towards Ms Le Pen.
Ms Le Pen on Friday morning called for all terrorist suspects to be expelled from France.
Another terrorist attack in Paris. The people of France will not take much more of this. Will have a big effect on presidential election!— Donald J. Trump (@realDonaldTrump) April 21, 2017
French voters will go to the polls on Sunday for the first round of their presidential election. Polls are currently on a knife-edge, with centrist candidate Emmanuel Macron battling conservative Francois Fillon, socialist Benoit Hamon, far-Left leader Jean-Luc Melenchon, and Ms Le Pen.
While other world leaders have refrained from speculating on the outcome, Mr Trump had no such reservations.
In an interview with The Associated Press later on Friday, Mr Trump said the attack played to Ms Le Pen's strengths.
"She's the strongest on borders and she's the strongest on what's been going on in France," Mr Trump said. "Whoever is the toughest on radical Islamic terrorism, and whoever is the toughest at the borders, will do well in the election."
US presidents typically avoid weighing in on specific candidates running in overseas election. But Mr Trump suggested his opinion was no different from an average observer, saying: "Everybody is making predictions on who is going to win. I'm no different than you."
Whether his apparent endorsement will help Ms Le Pen remains to be seen.
But on Twitter, many reacted angrily.
"Shut it, Donald," wrote one woman, Ines Helene, in French.
Another commented: "Shamefully taking political advantage of a terrorist attack."
And others pointed out that both Mr Trump and Ms Le Pen are widely believed to be the preferred candidates of the Kremlin.
Both have campaigned on a platform to upend the status quo, and both have challenged international organisations such as Nato and the EU.
Both are seen in Russia as sowing discord in their own country, while being more amenable to dealing with Moscow than their rivals.
Ms Le Pen openly celebrated the election of Mr Trump, calling the result an "additional stone in the building of a new world" and saying it boded well for her chances.
In January she visited Trump Tower, and was spotted eating in the fast food restaurant in the lobby - although it remains unclear whether she met Mr Trump himself.