President Donald Trump and North Korean leader Kim Jong Un met in Vietnam on Wednesday to continue negotiations on the denuclearization of the Korean Peninsula.

As Trump and Kim met, the president referred to Kim as a "great leader."

Kim is widely considered one of the world's most repressive rulers and was threatening the US with nuclear war not so long ago.

President Donald Trump on Wednesday told North Korean leader Kim Jong Un, who was threatening the US with nuclear destruction not so long ago, that he's a "great leader" as the two met in Hanoi, Vietnam.

"I think your country has tremendous economic potential," Trump said to Kim.

"I think you will have a tremendous future for your country, you're a great leader," Trump added. "We will help it to happen."

The president also said his relationship with Kim is a "really a good one."

Read more: Photos show how Trump's 2nd nuclear summit with Kim Jong Un is unfolding in Vietnam

"It's an honor to be with Chairman Kim, it's an honor to be together in Vietnam," Trump said as he met with the North Korean leader.

Kim is widely regarded as one of the most repressive leaders in the world and largely maintains power via a brutal system of prison camps.

In 2017, a judge who survived Auschwitz during the Holocaust said North Korea's camps are "as terrible, or even worse, than those I saw and experienced in my youth in these Nazi camps." The judge, Thomas Buergenthal, made this statement after hearing from former North Korean prison guards and prisoners.

Read more: The stories from inside North Korea's prison camps are horrifying

Kim is also the ruler of a country the US is still technically at war with.

Trump on Wednesday said "we'll see" when asked if he'd formally declare that the war is over as part of his negotations with Kim.

The two leaders are in Vietnam to continue discussions that started in Singapore last June over the denuclearization of the Korean Peninsula.

Trump has expressed optimism he can convince Kim to agree to give up his nuclear weapons, but experts and even some of his GOP allies in Congress have expressed doubts.

Read more: An ex-North Korea diplomat says Kim Jong Un won't ever give up nukes

Republican Sen. Marco Rubio on Wednesday tweeted, "I hope # TrumpKimSummit is a success. I fear it will be a dangerous failure."

In 2017, Trump and Kim routinely traded threats and insults from across the world, prompting fears a conflict would break out. They changed their tone in 2018, however, which prompted to the ongoing negotations that spiraled into their second face-to-face meeting in Vietnam.