Donald Trump told the Japanese prime minister that he could send him 25 million Mexicans to teach him about migration issues, according to reports.
The news of Mr Trump's comments, reported to have been made at the G7 conference, comes as the US president tweeted a collection of photos showing him looking chummy with fellow world leaders at the summit.
Mr Trump accused the "Fake News Media" of only showing "the bad photos (implying anger)" of the summit.
Since then, eyebrow-raising comments made by the US president have been reported by the Wall Street Journal.
In one meeting, Mr Trump raised the issue of migration as a problem in Europe and reportedly told Japanese Prime Minister Shinzo Abe: "Shinzo, you don't have this problem, but I can send you 25 million Mexicans and you'll be out of office very soon."
In another, during a conversation about terrorism, he is said to have told French President Emmanuel Macron that "You must know about this, Emmanuel, because all the terrorists are in Paris".
The President of the European Commission, Jean-Claude Junker, was asked by reporters to respond to Mr Trump repeatedly calling him a "brutal killer".
Mr Junker said "I think he meant it as a compliment but Im not so sure", over the comments which allegedly referred to Brussels' tax fines against US tech companies and blocks on America dealing directly with Germany and France for trade deals.
A photo of Mr Trump surrounded by disgruntled looking leaders at the summit went viral after the conference.
More from Donald Trump
I have a great relationship with Angela Merkel of Germany, but the Fake News Media only shows the bad photos (implying anger) of negotiating an agreement – where I am asking for things that no other American President would ask for! pic.twitter.com/Ib97nN5HZt
— Donald J. Trump (@realDonaldTrump) June 15, 2018
Now, a week later, the president followed up his claims that the situation was a "very friendly" one by publishing a series of photos on his Twitter account, some showing German Chancellor Angela Merkel and Canadian Prime Minister Justin Trudeau smiling.
Another photo shows the US president gripping Mrs May by the shoulder as she pats him on the arm.