President Donald Trump delivered a stern warning on trade to foreign countries at the Group of Seven summit on Saturday, advising trading partners not to retaliate against U.S. tariffs on the imports of steel and aluminum. "If they retaliate, they're making a mistake," Trump declared.

Trump told reporters he pressed for "fair and reciprocal" trade practices at the G7 meeting in Canada, urging his foreign counterparts to eliminate all tariffs, trade barriers and subsidies in their trading practices. The president has been at odds with key allies over the new tariffs, which dominated his talks with the leaders of major industrialized nations in the Canadian resort town. In addition to the U.S. and Canada, the group includes Britain, Italy, France, Germany and Japan.

Shortly before his arrival at the two-day summit, Trump injected additional controversy by suggesting that the G7 offer a seat at the table to Russia, which was ousted from the group after it annexed Crimea in 2014. The president said Saturday that re-admitting Russia to the elite club would be "an asset," telling reporters, "we're looking for peace in the world." Trump said he had not spoken with Russian President Vladimir Putin in a while.

Trump was departing the Canadian summit several hours early, heading to Singapore for his summit with North Korea's Kim Jong Un.

Who Is Howard X? Kim Jong Un Impersonator Detained At Singapore Airport Reuters

President Donald Trump said Saturday he has "a clear objective" for his upcoming nuclear summit with North Korea's Kim Jong Un, though he acknowledged that potential progress "will always be spur of the moment."

He described the meeting scheduled for Tuesday in Singapore as a "one-time shot" for Kim, and Trump said he was about to undertake a "mission of peace" as he left the Group of Seven meeting with world leaders in Canada.

The president told reporters that it's "so far, so good" as he headed into what he called "unknown territory in the truest sense." He said he thinks "it's going to work out very well."

Trump, who prides himself on his deal-making prowess, said he thinks he will know 'within the first minute" of meeting Kim whether the North Korean leader is serious about the nuclear negotiations.

"I think I'll know pretty quickly whether or not, in my opinion, something positive will happen. And if I think it won't happen, I'm not going to waste my time. I don't want to waste his time," Trump said.

It will be the first time that a sitting U.S. president and a North Korean leader have met.

Trump cited the unprecedented nature of the meeting and said he was convinced that Kim wants to do good things for his country.

"He could take that nation with those great people and truly make it great, so it's a one-time, it's a one-time shot, and I think it's going to work out very well," Trump said. "That's why I feel positive, because it makes so much sense."

He also praised the North Koreans, saying they have been "really working very well with us" during preparations for the summit.

"So far, so good. We're going to have to see what happens. I very much look forward to it," he said.

Trump hopes to persuade Kim to completely abandon the arsenal of nuclear weapons and ballistic missiles that the North Koreans have spent more than a generation amassing.

"I have a clear objective, but I have to say that it's going to be something that will always be spur of the moment. This has not been done before at this level. This is a leader who really is an unknown personality. People don't know much about him. I think that he's going to surprise on the upside, very much on the upside," Trump said.