WASHINGTON — President Donald Trump departed early from the Group of 7 summit in Canada Saturday after alienating many of the United States' closest allies with his aggressive trade declarations and surprising suggestion that Russia be readmitted to the exclusive group of major economic powers.

Trump left the Quebec resort where the group had gathered, leaving other world leaders uncertain about their future relationship with the U.S., to head to Singapore for a summit with North Korean leader Kim Jong Un Tuesday.

"I'll be on a mission of peace," Trump said at a news conference before he left.

He turned his attention to North Korea, saying he'd know "within the first minute" of his meeting with Kim whether the summit would be successful and that his approach to the objectives for the high-stakes meeting would be "spur of the moment."

"It's unknown territory in the truest sense, but I really feel confident," Trump said of the North Korean summit. "I feel that Kim Jong Un wants to do something great for his people. He has that opportunity and he won't have that opportunity again."

Trump left the United States' top allies in the G-7 rattled with startling statements such as a proposal that all the nations drop all their tariffs and trade restrictions even as he has risked a global trade war by imposing U.S. tariffs on a variety of products.

"I don't know if they were surprised with President Trump's free-trade proclamation, but they certainly listened to it and we had lengthy discussions about that," said Larry Kudlow, Trump's top economic adviser.

Trump denied that he was leaving the summit early because of tensions within the group and said his relationships with the other world leaders "is a 10."

But in he ripped into his G-7 counterparts, saying the U.S. is "like the piggy bank that everybody's robbing, and that ends." He vowed to control Iran's nuclear ambitions "with or without them" and warned other members to drop their trade barriers with the U.S.

"It's going to stop or we're going to stop trading with them," Trump said. "If they retaliate, they're making a mistake."

On Saturday morning, Trump arrived late for an 8 a.m. breakfast the world leaders held with the G-7's Gender Equality Advisory Council. His chair was empty as Canadian Prime Minister Justin Trudeau gave his opening remarks.

Trump had also arrived late to the summit on Friday, forcing the postponement of his bilateral meeting with French President Emmanuel Macron. He was skipping sessions on climate change and clean energy, and a working lunch to discuss protecting the world's oceans, to leave early Saturday.

Heading into the summit, the U.S. already had strained relations with leaders of the other nations in the G-7 _ Canada, the United Kingdom, France, Germany, Italy and Japan _ because of Trump's decision to impose tariffs on imported steel and aluminum and his threats to extend trade levies to automobiles from those nations.

Trump justifies the tariffs by accusing other nations of taking advantage of the U.S. in trade. He argues that they will force other nations to lower their own barriers for American goods.

But the U.S. imposes tariffs and quotas of its own to protect certain products, particularly tobacco and sugar. Trump's decision to bypass the World Trade Organization, set up to arbitrate tariff and other trade disputes, risks causing other nations to retaliate with protectionist measures that could damage the world economy.

Last year, Trump pulled the U.S. out of a sweeping Asian trade deal, the Trans-Pacific Partnership, struck by President Obama. He is threatening to walk away from the North American Free Trade Agreement with Canada and Mexico, which is being renegotiated at Trump's behest.

Both Trudeau and Macron, who talked with Trump privately in separate meetings Friday, were sharply critical of him leading up to the summit.

Trudeau called Trump's U.S. national security justification for steel and aluminum tariffs _ which implies Canada is a threat _ "insulting and unacceptable."

And Macron wrote on Twitter on Thursday that the other G-7 leaders may sign a summit memorandum to work on key issues, like trade and climate change, without Trump.

White House press secretary Sarah Huckabee Sanders described the meeting with Macron as "productive" and the one with Trudeau as "great."

"The two leaders and their delegations are close to a deal on NAFTA, but there was discussion of a bilateral deal," she said. Trump has said if a three-nation deal could not be reached, he would move to try to make separate deals with each country.

Before the session with Trudeau, who hosted the G-7 at a Quebec resort, Trump joked with him about the trade dispute.

"You know, Justin has agreed to cut all tariffs and all trade barriers between Canada and the United States. So I'm very happy about that," Trump said as Trudeau laughed.

"But we are actually working on it," Trump said, adding that the two sides had made a lot of progress Friday. "And I think we'll get to something very beneficial to Canada and to the United States."

Trudeau said it was "a pleasure" to host Trump.

"Obviously, trade has been a topic of discussion and will continue to be," Trudeau said.

Trump said the two did not discuss his suggestion that Russia rejoin the group. But Trump said Saturday that there was discussion at the summit about readmitting Russia.

"Something happened a while ago where Russia is no longer in. I think it would be an asset to have Russia back in," Trump said.

Russia was expelled from what at the time was the Group of 8 in 2014 after invading Ukraine and annexing Crimea. Before leaving the White House for Canada Friday morning, Trump surprised U.S. officials and allies by calling for Russia to be reinstated.

"Now, I love our country. I have been Russia's worst nightmare," Trump said. "But with that being said, Russia should be in this meeting. Why are we having a meeting without Russia being in the meeting?"

Although Italian Prime Minister Giuseppe Conte backed the idea, other G-7 leaders dismissed it. In the U.S., Democrats and some Republicans, including Sen. John McCain, R-Ariz., strongly objected to allowing Russia back into the group of advanced economies.

Trump told reporters Saturday that "some people like the idea of bringing Russia back in."

Pressed on whether Trump would require Russia to give up Crimea as a condition, Trump indicated he wouldn't, noting "they spent a lot of money on rebuilding it."

"Crimea was let go during the Obama administration. ... He allowed Russia to take Crimea. I may have had a much different attitude," Trump said. "With that being said, it's been done a long time."