While Vice President JD Vance was in Switzerland trying to reach a peace deal with Iran, it seemed like President Donald Trump was trying his utmost to undermine the talks.

After initial talks on Sunday, Vance told the media that progress had been made toward a future, noting, “We are looking to transform, fundamentally, the relationship with Iran.”

MS NOW analyst Richard Stengel, former undersecretary of state for public diplomacy and public affairs under President Barack Obama, agreed with network host Ayman Mohyeldin, who had praised Vance’s hopeful and optimistic statement, but then said Trump had broken a precedent that goes back thousands of years.

“I thought it was powerful and it was hopeful,” Stengel said. “And then Trump, you know, in the most puerile, adolescent way, you know, threatens the talks.”

While Vance was meeting with Iranian diplomats, Trump warned the delegation against keeping the Strait of Hormuz closed.

“You close it, and you won’t have a country,” Trump said on Fox News. “You won’t even make it back to your fucking country.”

“If there is one taboo in the history of diplomacy going back to the Peloponnesian War, is you do not threaten envoys, no matter how opposed you are,” he said. “And there he is, threatening envoys.”

Stengel said Trump didn’t simply break that precedent; he also violated the agreement he signed just days earlier.

“The number one plank in the Memorandum of Understanding says both parties must refrain from threats of force,” Stengel said. “He’s already violated that a dozen times.”

Check out the full conversation below: