It’s a remarkable change of tune for the United States. U.S. officials worked closely with G-7 negotiators for days on the communique, and other nations took pains to ensure that Trump would sign on, despite deep disagreements on trade.

Trump’s decision is likely to further divide the U.S. from its G-7 allies, who have long been skeptical of the president and have publicly and privately expressed deep frustration with Trump’s flippant comments and desire to overhaul their trade policies.

For Trump, the decision may be a political winner. The president’s base is deeply skeptical of the system of international cooperation that has for so long been at the core of U.S. foreign and economic policy.

Earlier in the day, Trump rated his relationship with G-7 leaders a perfect 10 — but the deep divide between the United States and some of its closest allies nonetheless shined through at the high-profile summit in Canada.

Even as Trump insisted he gets along just fine with his counterparts leading Canada, France, Germany, Italy, Japan and the United Kingdom, he further ostracized himself, arguing that Russia should be invited back into the exclusive international group and threatening to cut off trade relations with the G-7 nations if they don’t rethink what he says are unfair trade practices.

“The G-8 is a more meaningful group than the G-7,” Trump told reporters in a free-wheeling press conference before departing the continent for his historic meeting with Kim Jong Un.

Indeed, Trump did little to hide his distaste for the summit from the outset — arriving late to the summit on Friday and missing his first scheduled meeting with French President Emmanuel Macron and then joining a Saturday breakfast on gender equality after it had already started.

Soon after Trump boarded Air Force One, having cut short his time in Canada, German Chancellor Angela Merkel’s office distributed a photograph of G-7 leaders standing in a semi-circle with Trump sitting on the other side of a table with his arms crossed — an image that underscored Trump’s isolation.

Photos taken from other angles during the meeting appear to show a less dramatic scene, but the decision by Merkel’s office to release that picture was nonetheless seen as a symbol of what many in the international community have begun derisively referring to as a the “G6 +1.“

Trump’s ongoing efforts to strengthen ties with Moscow were perhaps the most unsettling for the West.

Russia was kicked out of the group, then the G-8, in 2014 for illegally annexing Crimea from Ukraine. Since then, Russia has been accused of meddling in the 2016 U.S. presidential election and poisoning a former Russian spy on British soil.

But Trump blamed former President Barack Obama, not Russian President Vladimir Putin, for the annexation of Crimea — adding that he may have done something different in response if it happened on his watch.

Trump’s comments were met with skepticism from many U.S. allies. “Before discussions could begin on any of this, we would have to ensure Russia is amending its ways and taking a different route,” British Prime Minister Theresa May said in a television interview on Friday after Trump first broached the issue.

Trump’s comments about bringing Russia back into the G-7 come as he is planning a summit with Putin. The Kremlin said Saturday that Vienna has been discussed as a possible venue for the meeting.

In the run-up to the G-7 summit, Trump told people close to him that he was dreading the meeting. The president hates being lectured to by other foreign officials and he tends to avoid one-on-one confrontations. Trump is more fixated on building relationships with powerful and domineering world leaders like Putin, Chinese President Xi Jinping and Kim, who he is eager to meet in Singapore.

Tensions over trade, meanwhile, dominated the summit. As POLITICO reported on Friday, Trump, during a private meeting, floated the idea of ending all tariffs and trade barriers between the U.S. and its G-7 allies. Right before leaving for Singapore, Trump upped the ante in his press conference with reporters, warning that he could cut off or severely limit trade access to the United States if G-7 countries don’t cooperate.

“We’re the piggybank that everybody is robbing,” Trump said. “And that ends.”

The Trump administration recently imposed tariffs on steel and aluminum imports from Canada, Mexico and the European Union, a decision that sent shockwaves throughout the world and resulted in a venomous response from key U.S. allies. Ahead of the summit, Trudeau called the decision “insulting” and “totally unacceptable.”

The U.S. imposed the tariffs on national security grounds, a rationale that offended close allies like Canada. But Trump refused to back away from that justification.

“It is our balance sheet, it is our strength, it is our national security,” he told reporters. “To have a great military, you need a great balance sheet.”

In his final press conference, Trudeau said people who expected the G-7 countries to resolve their differences with Trump on trade during the summit were expecting too much.

Trudeau also sharply disagreed with Trump’s comments from earlier Saturday that the NAFTA deal should have a clause that sunsets the agreement, signaling more future fireworks on trade between the two nations.

“There will be no sunset clause,” Trudeau said.

His words apparently set Trump off.

“PM 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!“

Every U.S. president has disagreements with other countries, even allies, but Trump’s tweet marked an unprecedented rebuke of the nation‘s neighbor and ally.

And it’s the latest example of Trump upending U.S. relations with longtime allies, and turning the tables on countries that have been dependable friends for decades.

Some G7 officials said Trump was too late. The communique was agreed, the summit done, the leaders packing up or already gone.

They noted the leaders’ declarations are typically not signed, simply agreed at the summit and published by the host country. The declarations had already been published and distributed to reporters at the summit site before Trump blastd out his tweets.

“We stick to the communique as agreed by all participants,” an EU official said.

Before Trump departed on Saturday morning, Trump had said that his relationships with other G-7 leaders could not be better.

“I would say the level of relationship is a 10,” he said. “We have a great relationship, Angela and Emmanuel and Justin.”

Trump also sought to cut through the tensions with some humor during the meeting.

“Justin has agreed to cut all tariffs,” he joked with reporters on Friday during his bilateral meeting with Trudeau.

When Trudeau was asked if he was disappointed that Trump decided to leave the summit early, Trump interjected. “He’s happy,” Trump said, sticking out his tongue to indicate he was joking.

David M. Herszenhorn contributed to this report from La Malbaie, Canada.