"China's been a big help, bigger than most people know," said the American president, before adding that he believed "North Korea is calling its own shots."
Kim and Chinese President Xi Jinping met several times in the past year. When Trump and Kim met for the first time in Singapore last June, the North Korean leader arrived in an Air China plane.
To get to Hanoi this week, Kim traveled by train through China and some reports said he may have made a stop in Beijing. It isn't clear whether he met Xi during his travels, nor if he plans on meeting the Chinese leader soon.
North Korean state media KCNA said a delegation led by the reclusive state's Vice Minister Ri Kil-Song has left for China. China's foreign ministry said it hopes dialogue and communication between the U.S. and North Korea can continue.
Trump said he believed China "can't love having a nuclear state" right across its borders and that Beijing would want to see "the problem solved."
On the U.S.'s trade relations with China, Trump said the American economy is thriving: The stock market has gone up, and domestic unemployment numbers have improved. The president also claimed that additional tariffs implemented on Chinese goods have helped to reduce the U.S. trade deficit.
Trump announced over the weekend that due to progress made in the U.S.-China trade talks, he's delaying the implementation of additional tariffs on Chinese products initially planned for early-March.
The summit between Trump and Kim in Hanoi, which ended on Thursday, was cut short. The American president said that's because both sides could not agree on sanctions.
Trump had repeatedly said at the start of Thursday's talks that his relationship with Kim was strong, and that he expected that connection to eventually carry the two nuclear powers to an agreement.
Although both sides say they've been making progress in recent months, this round of top-level talks focused on many of the same issues as last June's Singapore summit.
Trump is pushing North Korea to give up its nuclear weapons as he dangles the prospect of an economic boost to the repressive country. Kim wants to see sanctions eased or lifted — but without losing the strategic benefits of his weapons of mass destruction.
— Reuters contributed to this report.