Here are some memorable barbs from Trump, who has brazenly defied traditional diplomatic convention not to speak ill of allies in public:

- FRANCE -

Trump had once seen Macron as a budding friend, with the two inviting each other for high-profile visits, but the tycoon president was apparently incensed by the French leader's rejection of Trump-style nationalism in a speech marking 100 years after the end of World War I.

Trump, whose Armistice Day trip to Paris drew domestic criticism after he skipped a cemetery visit due to rain, ridiculed Macron for his low approval rating and said there was "no country more nationalist than France."

He threatened to slap tariffs on French wine and again criticized Macron for supporting European-wide defense outside NATO, the alliance to which Trump says the United States pays too much.

- CANADA -

Trump has shown open disdain for the youthful, left-leaning prime minister of Canada, Justin Trudeau, as the US president revises the North American Free Trade Agreement, which he sees as hurting US manufacturing and farming.

Trump refused to sign a customary statement by the Group of Seven industrial nations after a June summit in Quebec led by Trudeau.

Leaving early to meet with North Korean dictator Kim Jong Un, Trump tweeted that Trudeau was "very dishonest and weak" and had acted "mild and meek" in meetings before criticizing US tariffs at a news conference.

- GERMANY -

Trump's relationship was strained from the start with Chancelor Angela Merkel, who unlike Macron did not attempt to forge a chummy relationship with the right-wing populist.

Trump has repeatedly intervened rhetorically in Germany's sensitive debate over immigration, after Merkel in 2015 opened Germany's borders and ultimately let in more than one million asylum seekers.

Trump in June tweeted that Germans were "turning against their leadership" over the "big mistake" on immigration and incorrectly said that crime was "way up" in Germany.

- BRITAIN -

Despite Prime Minister Theresa May's efforts to preserve Britain's "special relationship" with the United States, Trump has openly criticized her handling of her top issue -- Britain's planned exit from the European Union.

Just as he was visiting Britain this year, on an invitation for which May faced domestic criticism, Trump told a London newspaper that May's party rival Boris Johnson would be a "great prime minister" and poured cold water on May's hopes for a trade deal with the United States if Britain stayed in the EU single market.

Trump has also repeatedly assailed London Mayor Sadiq Khan, who is Muslim, taking out of context Khan's calls for calm after an attack and then calling Khan's explanation "pathetic."

- AUSTRALIA -

Trump opened on the wrong foot with Australia, one of the most pro-US countries which boasts of fighting alongside the United States in every major conflict in modern times.

Trump hung up on Australia's then prime minister, Malcolm Turnbull, after brusquely criticizing a deal on refugee settlement reached under previous US president Barack Obama, according to The Washington Post.

The two leaders later appeared to patch up through a series of friendly encounters, arranged in part by Rupert Murdoch, the Australian-born media mogul who owns Fox News, Trump's favorite channel.

- MEXICO -

Trump launched his presidential campaign by branding undocumented Mexican immigrants as criminals and has maintained racially charged rhetoric since entering the White House.

Trump, however, has been unusually restrained in his public remarks about Mexican President Manuel Lopez Obrador and his predecessor Enrique Pena Nieto, who reportedly had a contentious phone call with the US leader.

- JAPAN, SOUTH KOREA -

Trump has managed cordial public interactions with the leaders of key Asian allies Japan and South Korea but has been blistering in his criticism of their trade policies.

Trump at a news conference last week said that Japan "has treated us very unfairly" and, according to The Washington Post, startled Prime Minister Shinzo Abe during a June summit by quipping, "I remember Pearl Harbor," imperial Japan's 1941 sneak attack on the US Pacific fleet.