Donald Trump acts like a "drunk tourist" who "steps on others without realising it" when it comes to diplomacy, a state department official has claimed after the president left a G7 Summit in Italy, in which he frustrated leaders in attendance.

Trump's performance in the last leg of his first international trip left other world leaders fuming with his stances on climate change, taxes and security.

But it was his "arrogance" in threatening to oppose the Paris Agreement that was "an abdication of American leadership", the official said, according to Daily Mail.

"When it comes to diplomacy, President Trump is a drunk tourist," the State Department official told the Daily Beast. "Loud and tacky, shoving his way around the dance floor. He steps on others without realising it. It's ineffectual."

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The official, who has not been named, said that the United States should be 'out front' when it comes the Paris Agreement.

"One hundred and ninety-five nations never agree on anything, so when they do, accepting the measure should be easy," the official said. "The United States needs to be out front on this pact."

Six of the seven G7 nations agreed to stick with their commitment to implement the 2015 Paris Agreement aimed at slowing global warming, but Trump said he needed more time to decide if the United States would abandon the accord.

His administration has argued that US emissions standards are tougher than those set by China, India and others, and therefore have put American businesses at a disadvantage.

Near the end of the summit, he tweeted teasingly that he would make a decision on Paris next week, leaving delegations to scratch their heads about why he could not commit in Taormina.

Italian Prime Minister Paolo Gentiloni, who chaired the meeting, said the other six "won't change our position on climate change one millimeter. The US hasn't decided yet. I hope they decide in the right way."

Six of the seven G7 nations agreed to stick with their commitment to implement the 2015 Paris Agreement aimed at slowing global warming. Photo/AP
Six of the seven G7 nations agreed to stick with their commitment to implement the 2015 Paris Agreement aimed at slowing global warming. Photo/AP

Gentiloni said climate was "not a minor point" and that he hoped the United States would decide "soon and well" because the Paris accords "need the contribution of the United States".

"I found him very willing to engage, very curious, with an ability and desire to ask questions and to learn from all his interlocutors," said Gentiloni, the G7 summit's host.

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German Chancellor Angela Merkel was more downbeat, calling the G-7 climate talks "very unsatisfactory".

The G7 leaders meeting in Sicily vowed to fight protectionism, reiterating "a commitment to keep our markets open", despite the Trump administration's talk of an "America first" policy and continued criticism of Germany for its huge trade surplus.

They also agreed to step up pressure on North Korea, to forge closer cooperation in the fight against terrorism, and on the possibility of imposing more sanctions on Russia over its role in the conflict in Ukraine.

The G-7 summit came after Trump confounded hosts at NATO headquarters in Brussels earlier in the week.

The appearance was described as a "disaster" by more than one European official.

With the leaders of America's NATO partners standing like school children behind him, Trump upbraided them for not spending more on defence and repeated the charge that some members owed "massive amounts of money' from past years - even though allied contributions are voluntary.

Trump engaged in two alpha-male handshakes with France's new 39-year-old President Emmanuel Macron, who seemed to get the better of Trump on both occasions. Photo/AP
Trump engaged in two alpha-male handshakes with France's new 39-year-old President Emmanuel Macron, who seemed to get the better of Trump on both occasions. Photo/AP

At one point during his time in Brussels, he muscled aside Montenegrin Prime Minister Dusko Markovic as NATO leaders walked into the alliance's new headquarters for a photo session.

And he engaged in two alpha-male handshakes with France's new 39-year-old President Emmanuel Macron, who seemed to get the better of Trump on both occasions.

Macron praised Trump's "capacity to listen" and his "intention to progress with us".

But Macron said he told the US President that it was "indispensable for the reputation of the United States and the interest of the Americans themselves that the United States remain committed" to the Paris agreement.

Trump's appearance in Brussels was particularly galling to the Germans, who after months of painstaking relationship building with Trump - including Merkel's invitation to his daughter Ivanka for a G20 women's summit in Berlin - found themselves under attack from him on two fronts.

Before heading to NATO, Trump criticised Germany's trade surplus in a private meeting with senior European Union officials.

The macho posturing in Europe contrasted to the images, a few days earlier, of Trump and his team swaying, swords in hand, with the absolute rulers of Saudi Arabia at a lavish welcome ceremony given by King Salman.

Summing up the tour on Saturday, Trump's advisers seemed most enthused about the Saudi leg, where he clinched a $110 billion arms deal and forged what one aide described as a "personal bond" with the king.