During Donald Trump’s time as president, a balancing act (of sorts) developed between the U.S. and North Korea. There is even the possibility that a major crisis between the two countries was avoided but despite this, North Korea under the leadership of Kim Jong-un continued to develop its nuclear and missile capabilities, The Conversation reports.

In view of this, South Korea’s president Moon Jae-in is critical of the former president’s efforts to denuclearize the Korean Peninsula, Axios reports. In an interview with The New York Times, he said Trump did little more than “beat around the bush” with North Korea and “failed to pull it through.”

Moon is in his final year as president and is clearly worried about the situation. He’s said denuclearization is a “matter of survival” for South Korea. He is calling for President Joe Biden to restart negotiations with Kim Jong-un, which have been stalled for the past two years.

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

Then he criticized what Trump left unfinished.

“He beat around the bush and failed to pull it through,” Moon said. “The most important starting point for both governments is to have the will for dialogue and to sit down face to face at an early date.”

The South Korean leader also expressed hope that the U.S. will forge a better relationship with China, especially in regards to North Korea and other issues, and warned that if “tensions between the United States and China intensify, North Korea can take advantage of it and capitalize on it.”

Early in Trump’s presidency, talks between the U.S. were off to a good start, with Trump being the first sitting president to set foot on North Korean soil to shake hands with Kim. The situation soured however when both countries failed to reach a substantive agreement on denuclearization and reducing sanctions.

It’s understandable that Moon is worried because when Biden became president when North Korea’s Kim Yo-jong (sister of Kim Jong-un) warned the U.S. to “refrain from causing a stink” if “it wants to sleep in peace for coming for years.”

North Korea has also conducted its first major weapons test since Biden took office, launching two ballistic missiles into the East Sea in March.

If you’ve ever wondered why North Korea remains antagonistic towards the U.S., this Washington Post article lays the situation out pretty plainly. The relationship between the U.S. and North Korea has been a rocky one, full of pain on both sides. I’m hoping for a better situation now but I really don’t know what will happen.