President Donald Trump’s rhetoric on North Korean nuclear aggression has been widely criticized for being too inflammatory, but former United Nations Secretary-General Ban Ki-moon said he believes the Republican’s underlying message is inherently the right one.

“I know there are some different interpretations on what President Trump has been saying, but his underlying message has been clear: While he’s ready to engage in dialogue, such North Korean behavior will never be tolerated,” Ban told CNBC on Thursday.

The president has “shown a strong message of deterrence … It is the right message,” he said on the sidelines of the Barclays Asia Forum.

In early October, Trump publicly declared that diplomatic talks with North Korean leader Kim Jong Un were a waste of time — even as Secretary of State Rex Tillerson said Washington had active lines of communication to Pyongyang.

The possibility that Kim’s regime may soon be capable of attaching a nuclear warhead to an intercontinental ballistic missile has unnerved the White House, which said in April that its official North Korea policy was “maximum pressure and engagement.”

“This is the worst security situation since the end of the Korean War,” Ban said.

He added that he appreciates Trump’s upcoming five-nation Asia visit at such a critical time and hopes Washington, Seoul, Tokyo and Beijing can come up with a common strategy to peacefully halt North Korean violations of U.N. resolutions.

Ban, a South Korean national, was widely expected to run for the presidency in his home country earlier this year, but he ultimately did not enter the race.

Commenting on South Korean President Moon Jae-In’s performance regarding Korean Peninsula tensions, the former U.N. head said Seoul was closely coordinating and consulting with Trump, Japanese Prime Minister Shinzo Abe and Chinese officials.

Ban himself said he has been urging South Koreans to show “a very strong message at this time.”

Given the strategic relationship between Beijing and Pyongyang, the mainland can do more to reign in the rogue state, the 73 year-old continued, identifying political pressure as an example.