President Trump is attending the dinner with European leaders at the onset of the G-7 summit this week, amid an escalating trade war with China and days of bashing American allies. The G-7, which is being held in France, includes the U.S. as well as Canada, France, Germany, Italy, Japan and the United Kingdom.

Mr. Trump had lunch with French President Emmanuel Macron on Saturday and held an impromptu pool spray. Macron said topics at the summit would include Iran, the economy, and climate. Speaking to reporters, Mr. Trump highlighted the "special relationship" between the U.S. and France.

After the lunch, Mr. Trump tweeted that "many good things are happening for both of our countries." He initially tagged a parody account instead of Macron in his tweet, although he later corrected it with a new tweet tagging the real Macron.

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The White House said in a press release that Mr. Trump will "work with G-7 allies to build a future of opportunity with all our nations" at the summit this week. Priorities for the White House include tackling "the rise of unfair trade practices to achieve free, fair and reciprocal trade."

President Trump sits to lunch with French President Emmanuel Macron, at the Hotel du Palais in Biarritz, France, on August 24, 2019. Ludovic Marin / AFP/Getty

In recent days, Mr. Trump has revived his suggestion that Russia should be reinstated into the group of seven leaders of major advanced economies, blaming former President Obama for allowing Russia to annex Crimea. Mr. Trump sometimes suggests America's friends treat her worse than her enemies, particularly on trade, a worldview and approach to international politics that critics say sends the wrong signal to a watching world.

"Our allies take advantage of us far greater than our enemies," the president told his audience at a manufacturing plant in Pennsylvania earlier this month.

Earlier this week, the president unloaded on Denmark's prime minister for suggesting Greenland is indeed not for sale, describing her comments as "nasty" and suddenly canceling his trip to Denmark. He's also laid into Britain, France and Germany for not taking back ISIS fighters captured in Syria, threatening to release the fighters back into those countries.

The president has also voiced intense frustration with Macron over trade-related issues, even threatening to place tariffs on French wines.

"France just put a digital tax on our great American technology companies," the president tweeted last month. "If anybody taxes them, it should be their home Country, the USA. We will announce a substantial reciprocal action on Macron's foolishness shortly."

Mr. Trump, who does not drink alcohol, added, "I've always said American wine is better than French wine!"

Last year, the G-7 summit became six against one, as Mr. Trump refused to sign the traditional agreement at the end of the summit and left early amid disputes over trade. He appeared to get along well with all the leaders publicly during his visit — before unleashing angry tweets after Air Force One had landed. He expressed particular ire at Canadian Prime Minister Justin Trudeau.

"Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, 'US Tariffs were kind of insulting' and he 'will not be pushed around.' Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!" Mr. Trump tweeted after the conclusion of last year's summit.

The leaders will not sign a joint agreement this year, but they are set to discuss the global economy, Iran, and whether Russia should rejoin the group after it was kicked out in 2014 over the annexation of Crimea. Mr. Trump's first meeting will be with Britain's new prime minister, Boris Johnson, on Sunday morning.

Paula Reid, Grace Segers and Kathryn Watson contributed to this report