South Korean President Moon Jae-in during an interview with the New York Times said that former President Donald Trump “failed” on the issue of the denuclearization of the Korean Peninsula. “He beat around the bush and failed to pull it through,” Moon said, referring to Trump’s efforts to get North Korea to give up its nuclear weapons.

Trump did not immediately respond to a request for comment from Insider.

During his single term in the White House, Trump met with North Korean leader Kim Jong Un several times to discuss denuclearization. His interactions with Kim were historic — Trump was the first sitting U.S. president to enter North Korea.

But by the time Trump left office, the rogue state had not given up a single nuclear weapon. North Korea has also continued provocative missile tests.

Though he was critical of Trump’s efforts on North Korea, Moon during his interview with the Times urged President Joe Biden to engage with Pyongyang to succeed where his predecessor failed. Moon emphasized that denuclearization is a “matter of survival” for South Korea.

“I hope that Biden will go down as a historic president that has achieved substantive and irreversible progress for the complete denuclearization and peace settlement on the Korean Peninsula,” Moon said.

In late March, the White House said Biden was unlikely to pursue a face-to-face meeting with Kim, though the president has signaled he’s open to diplomacy with North Korea.

Trump excoriated Moon over his comments in a statement on Friday.

“Kim Jong-un of North Korea, who I have gotten to know (and like) under the most trying of circumstances, never respected the current president of South Korea, Moon Jae-in. I was always the one who stopped the aggression toward the South, but unfortunately for them, I am no longer there,” Trump said.

The former president went on to say that Moon was “weak as a leader and as a negotiator, except when it came to the continued, long-term military ripoff of the U.S.A. (as is the case with many other countries we protect!).”

Critics of Trump have said his meetings with Kim helped legitimize one of the world’s most repressive leaders while offering virtually no benefits to the U.S. or its allies.

Trump’s relationship with Kim was controversial and perplexing to foreign policy experts. Early on in his presidency, he traded numerous threats and insults with the North Korean leader from across the globe — sparking fears of a nuclear war. But Trump’s tone shifted drastically in 2018 ahead of his first summit with Kim. Over the rest of his time in office, Trump repeatedly showered Kim with praise and referred to him as a “friend.”

Trump’s amicable demeanor toward Kim, who maintains power largely via a system of concentration camps, frequently led to criticism in Washington and beyond.

In a recent interview with Fox News’ Sean Hannity, Trump defended his relationship with Kim.

“When I came in President Obama said… ‘the biggest problem we have is North Korea. There’s going to be a war’. There was no war, we got along great,” Trump told Hannity. “[Kim Jong Un] writes me letters. I like him, he likes me. There’s nothing wrong with that.”