The climate accord was the most vivid sign of division between the United States and his allies, but it was not the only one: Mr. Trump also scolded Germany for its trade practices and lectured NATO members for not adequately supporting the alliance.
“There was a lot of give-and-take between the different countries in the room,” said Gary D. Cohn, director of the National Economic Council. But he insisted that the other countries understood Mr. Trump’s refusal to decide now, even if they did not support that position.
“The president’s only been in office for a certain period of time, and they respect that,” Mr. Cohn said. He added: “We’re all allies. We’re all trying to get to the right place and be respectful of each other.”
While Mr. Trump’s decision was not a surprise, the reaction was swift and critical.
Alden Meyer, director of strategy and policy at the Union of Concerned Scientists, said: “President Trump’s continued waffling on whether to stay in or withdraw from the Paris Agreement made it impossible to reach consensus at the Taormina summit on the need for ambitious climate action. But he stands in stark isolation.”
The leaders of Germany and France expressed disappointment, according to The Associated Press. “The whole discussion about climate was very difficult, not to say unsatisfactory,” Chancellor Angela Merkel of Germany said. “There’s a situation where it’s six — if you count the European Union, seven — against one.”
President Emmanuel Macron of France said he had told Mr. Trump it was “indispensable for the reputation of the United States and for the Americans themselves that the Americans remain committed” to the climate agreement.
The G-7 statement provides the United States more time to resolve internal White House debates about whether to pull out of the pact. It says the United States is “in the process of reviewing its policies on climate change and on the Paris Agreement and thus is not in a position to join the consensus on these topics.”
The president did not mention the impasse in his only public remarks after the summit, to American troops at the Sigonella Naval Air Station in Sicily. But he repeated his complaints about trade and the financing of NATO, even as he pronounced the trip a rousing success.
“We hit a home run no matter where we are,” he said.
For Mr. Trump, however, the lack of a decision on the climate accord put an uncertain ending on an ambitious first presidential trip that began as a respite from the surfeit of scandal at home.
Beleaguered White House aides — who were aboard Air Force One flying to Riyadh, Saudi Arabia, when they heard the allegations that Mr. Trump had called his F.B.I. director a “nut job” — hoped the trip would be a much-needed change of subject.
To some degree, it was, if only because the White House engineered the itinerary to keep Mr. Trump far away from reporters who could ask him questions. They scheduled no news conferences and put the president only in highly controlled situations: a brief photo session with a foreign leader; a teleprompter speech; ceremonial gatherings with other leaders.
But on Saturday, as his aides tried to promote the trip’s accomplishments, reporters bombarded them with questions about reports that Mr. Trump’s son-in-law, Jared Kushner, had talked about opening a secret back channel to Russia during the transition.
“We’re not going to comment on Jared,” an exasperated Mr. Cohn said.
In some ways, it was not one trip, but two, each with very different themes.
In Saudi Arabia and Israel, Mr. Trump was surprisingly disciplined, sticking to his script and delivering two speeches that set a clear course for his approach to the Middle East. His rapturous welcome in both countries suggested the United States could make a new start with allies who had grown restive during the Obama administration.
In Europe, however, the pugnacious side of Mr. Trump reasserted itself. In addition to his harangue of NATO members on budgetary matters, he declined to explicitly reaffirm America’s commitment to Article 5, which requires the United States to come to the defense of allies in the event of an attack.
He also won derisive headlines across the Continent after muscling the prime minister of Montenegro aside during a photo shoot, an image that quickly became a metaphor for his rough dealings with Europeans.
“His advisers tried to make him understand that there are some allies that are really nervous and needed reassurance,” said Volker Perthes, the director of the German Institute for International and Security Affairs. “He managed to do it with the Saudis and the Israelis.” But in Europe, he said, “he does take us for granted.”
Brian McKeon, a senior policy official in the Pentagon during the Obama administration, said, “the in-your-face thing at the NATO headquarters was pretty undiplomatic. He succeeded at busting norms but not building good will.”
But the national security adviser, Lt. Gen. H.R. McMaster, pushed back on that, saying that Mr. Trump’s participation in the ceremony was an implicit endorsement of Article 5. “He did not make a decision not to say it,” General McMaster said.
On climate, Mr. Trump has long railed against what he said were the economic dangers of a global climate pact. He has demanded more flexibility in setting standards on emissions, saying other countries were getting a better deal and that the agreement could be costly for American businesses.
In a message on Twitter on Saturday, Mr. Trump said: “I will make my final decision on the Paris Accord next week!”
There is an intense debate inside the West Wing over whether to withdraw from the accord or to try to renegotiate its terms, pitting hard-line nationalists, like the chief strategist Stephen K. Bannon, against more mainstream advisers like Mr. Cohn.
On Thursday, Mr. Cohn told reporters that Mr. Trump’s thinking on the subject was “evolving.” But other senior officials said even if the United States remained in the agreement, it could effectively gut its principles.
The exit of the United States, the world’s second-largest greenhouse gas polluter after China, would not immediately dissolve the pact, which was negotiated under President Barack Obama and legally ratified last year. But it would profoundly weaken the strength of the deal and pave the way for other countries to withdraw from it.
Some climate diplomats noted that the rest of the world was growing weary of America’s back-and-forth on climate change policy. In 1997, the United States joined the world’s first climate treaty, the Kyoto Protocol, but later withdrew during the Bush administration.
“At some juncture, other countries are going to get sick of us joining in, pulling out, joining in and pulling out and say, ‘Are we really going to work with the U.S. on this anymore?’” said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton.
Mr. Trump’s supporters, particularly coal state Republicans, are eager for him to withdraw from the Paris accord, seeing such a move as a fulfillment of a signature campaign promise. Speaking to a crowd of oil-rig workers last May, Mr. Trump vowed to “cancel” the agreement.
Coal miners and coal executives in states like Kentucky and West Virginia have pushed hard for Mr. Trump to reverse all of Mr. Obama’s climate change policies, which are ultimately aimed at reducing the widespread use of burning coal.
In a recent letter to Mr. Trump from 10 state attorneys general, West Virginia’s attorney general, Patrick Morrissey, wrote, “Withdrawing from the Paris Agreement is an important and necessary step toward reversing the harmful energy policies and unlawful overreach of the Obama era.”
On trade, Mr. Trump pushed his demand that any trade agreements the United States negotiates must be fair, as well as free. The Trump administration has taken particular aim at Germany, accusing it of depressing the value of the euro to make its exports more competitive and to undercut American goods.
In a meeting with leaders of the European Union in Brussels on Thursday, Mr. Trump complained about imports of German cars, threatening to stop them and calling Germany “very bad” on trade.
German officials point out that its two leading luxury automakers, BMW and Mercedes-Benz, have huge assembly plants in the United States. They are also frustrated that Trump officials repeatedly raise the prospect of negotiating a bilateral trade agreement with Germany, something that the country, as a member of the European Union, cannot do.
Shortly after Air Force One took off from Sicily for Washington, Mr. Trump said on Twitter that he had enjoyed “great” meetings on trade, saying, “we push for the removal of trade-distorting practices…to foster a truly level playing field.”