The Trump attack came only hours after divisions opened up elsewhere in the alliance, with Turkey vowing to oppose a North Atlantic Treaty Organisation plan to defend Baltic countries unless the alliance backs it in recognizing the Kurdish YPG militia as a terrorist group.
Brits have reason to expect fireworks.During past visits, Trump has made controversial comments about the NHS, repeatedly insulted London's mayor, Sadiq Khan, and gave a surprise newspaper interview humiliating his then host, former Prime Minister Theresa May.Meanwhile, just 19 percent of Brits have a positive opinion of Trump, according to the pollster YouGov.
On US trade spat with France, Trump said, however, that it should be possible to rapidly resolve it.
"What we are now experiencing is the brain death of NATO", Macron told magazine in the wake of the United States' decision to withdraw troops from northeast Syria.
Images soon began circulating on social media of multiple occasions that Mr Trump and Prince Andrew had been photographed together over the years, even shared by the Duke of York's official Twitter account as recently as June 4. Trump and Macron are due to meet on the sidelines of the summit.
In turn, Turkish President Recep Tayyip Erdogan has lashed out at Macron, and the very public arguments bode ill for a summit hosted by British Prime Minister Boris Johnson, who is deep into an electoral campaign and desperately wants to smooth things over.
Lashing out at Paris for a digital service tax that he said unfairly discriminates against United States tech companies - including Google, Apple, Facebook and Amazon - Trump repeated announcements that taxes are set to rise on French products, including cheese, wine and other products, as a measure of new to-be-introduced trade tariffs.
Mr Trump said he is weighing issuing sanctions against Ankara if they move forward with plans to buy the weapons.
But the US leader's broadside came only hours after splits opened up elsewhere in the alliance, with Turkey threatening to block a plan to defend Baltic states unless the alliance backs it in recognising the Kurdish YPG militia as a terrorist group.
That threat raises new questions about NATO's commitment to its collective defence clause - Article 5 - under which all allies vow to come to the aid of a member under attack. The clause has only ever been activated once, after the 9-11 attacks in the United States.
Some lawmakers have proposed censure in recent days as a way to denounce Trump without forcing him from office. One short working session will be held at a golf resort in outer London on Wednesday.
Explicitly linking his complaint that Europe does not pay enough for NATO's security missions to his staunch "America First" defense of US commercial interests, Trump said it was time for Europe to "shape up" on both fronts.
Macron, Erdogan and German chancellor Angela Merkel will be received at Downing Street later on Tuesday by Johnson.
While giving few specifics, Trump said he believed Russian Federation wanted deals on arms control and nuclear issues, and that he would be willing to bring China into such accords.
"So we can make a deal, we can take a harsh approach and solve that problem instantaneously if we wanted to. China. We may bring them in later, or we may bring them in now".