President Donald Trump sided with North Korean leader Kim Jong Un over long-time ally South Korea on Friday.

Kim explained in a letter to the president that recent missile tests were in response to US-South Korean joint military exercises.

"He wasn't happy with the war games," Trump said. "You know, I've never liked it either," Trump added.

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President Donald Trump said Friday that he received a "very beautiful" letter from North Korean leader Kim Jong Un explaining that recent missile tests were a response to US-South Korean war games, joint military exercises Trump says he's "never liked."

North Korea has conducted multiple weapons tests in recent weeks, during which North Korea tested a new type of short-range ballistic missile apparently designed to skirt South Korean defenses.

"He wasn't happy with the war games," Trump said, according to AFP. "You know, I've never liked it either," he, agreeing with the young dictator over a long-time ally.

Read more: North Korea is not only firing off new missiles — it may also be learning to launch them faster

Trump has repeatedly downplayed North Korea's testing. Instead, he has been lashing out at South Korea.

The US and South Korea began joint military exercises earlier this week. The Dong Maeng exercises are scaled-down computer-based training exercises being held for only the second time in place of larger exercises done in the past, but North Korea still considers them to be a provocation.

The US and South Korean militaries have not held any large-scale war games since June of last year, when the president said he wanted to halt joint military exercises that he considered "tremendously expensive" and "provocative."

Talking about the exercises Friday, Trump said, "I never liked it. I don't like paying for it ... We should be reimbursed for it," Yonhap News Agency reported.

Trump and Kim after their summit at the Capella Hotel on Sentosa island in Singapore. Jonathan Ernst/Reuters

The president's comments come just one day after he again criticized South Korea for not paying its fair share for US defense commitments.

"We've been helping them for about 82 years and we get nothing. We get virtually nothing," Trump said Thursday, explaining that he is pushing South Korea to pay more. "They've agreed to pay a lot more, and they will agree to pay a lot more than that," he added.

"The US-South Korean alliance was forged in blood during the crucible of the Korean War," Bruce Klingner, a senior research fellow at the Heritage Foundation, told CNN. "Its enduring motto is 'katchi kapshida' — 'we go together' — not 'we go together, if we are paid enough.'"

"2019 is weird," Vipin Narang, a political science professor at the Massachusetts Institute of Technology, told CNN. "The president has more respect for Kim Jong Un than he does for South Korea ... our formal ally."

Trump has met Kim three times, yet none of the meetings have moved the ball forward on denuclearization. Trump suggested Friday that another meeting may be possible. Secretary of State Mike Pompeo said Wednesday that the US remains hopeful that negotiations can continue despite North Korea's decision to conduct missile testing.