Seeing released prisoners from North Korea 'one of the greatest joys of my life,' Pence says

On the heels of North Korea's release of three American citizens, Vice President Mike Pence touted Donald Trump's leadership in the negotiation process.

Pence told ABC News' Johnathan Karl in an interview Thursday morning that seeing the three men just released by North Korea "was really one of the greatest joys of my life."

"I think it is a direct result of President Trump's leadership on the world stage," Pence said. "Sending these three Americans home before any concessions have been offered I think is a testament to the president's policy of peace through strength -- strong, clear, American leadership with our allies at the table has brought us this far, and we hope it opens the way to a lasting peace."

The three men, Kim Dong Chul, Kim Hak Song and Kim Sang Duk, also known as Tony Kim, each had been detained for more than a year before arriving in the U.S. early Thursday morning.

Pence told Karl it was "heartbreaking" to consider the plight of one of the three men who was sentenced to hard labor.

Karl used Trump's own words when asking Pence if he believed Kim Jong Un is a "madman." Pence did not directly answer, but he said there is reason to be optimistic.

"We’re seeing hopeful signs from Kim Jong Un that he is prepared to embrace complete denuclearization -- that's his words,” Pence said.

When pressed by Karl on whether Kim can be believed, Pence said, "We all understand the record of the Kim regime."

"If he will change, different from his father, different from his grandfather, if he will set his nation on a different path, that there's a bright future available for the people of North Korea," the vice president added.

Karl also asked Pence about Secretary of State Mike Pompeo’s second visit to North Korea, during which he met with Kim Jong Un.

"Well," the vice president responded, "what you're seeing is diplomacy, but diplomacy that has followed the United States of America speaking truth. That we'll no longer tolerate the path that North Korea has been on in regards to nuclear missiles."

North Korea, until recent discussions with South Korea, didn't appear as if it would consider tolerating some 28,000 U.S. troops remaining on the peninsula. Defense Secretary Jim Mattis has said removing American forces shouldn't be part of any negotiations with North Korea.

"There has been no discussion about that, and we don't anticipate that," Pence told Karl. "The hopeful sign here is that, again, very different from the past, with no concessions by this administration, offered or spoken about."

"[Kim] didn't object to our military exercises with South Korea, which has historically been objected to by North Korea," Pence continued. "We hope this means this is the beginning of a new moment, but we won't know that, the president believes, until he sits down, looks him in the eye, makes our expectations clear and determines what their intentions are."

Closing the interview, Pence was asked whether the Trump administration is willing to see another war in the Middle East if Iran restarts its nuclear program.

Pence replied: "The United States of America will not permit Iran to obtain a nuclear weapon."

Pressed further for a direct answer, Pence added: "I think it's absolutely imperative, and it's clear that we cannot permit Iran to ever obtain a nuclear weapon. But let me be clear on this point -- we hope for better."

ABC News' Morgan Winsor contributed to this report.