Kim Jong-un said he would not be holding a second summit with US President Donald Trump if there was no chance of North Korea giving up its nuclear ambitions.
The two leaders began a second day of talks earlier on Thursday in the Vietnamese capital, Hanoi, with both expressing hope for progress on improving relations and the key issue of denuclearisation.
“If I’m not willing to do that, I won’t be here right now,” Kim told reporters through an interpreter, when asked if he was ready to give up his nuclear weapons.
Trump, responding to that, said: "That might be the best answer you’ve ever heard.”
The two leaders were sitting across from each other at a conference table, with their aides.
Kim did not elaborate on what "denuclearisation" would entail, but asked if he was ready to take concrete steps, Kim said they had just been talking about that.
"Hope you give us more time to talk. Even a minute is precious," he told reporters.
After a dinner on Wednesday, the two men started a series of meetings in which Mr Trump was expected to make the case that North Korea would be best served by pursuing prosperity rather than its nuclear weapons programme.
President Kim also said he would welcome Washington opening a liaison office in Pyongyang.
Asked if he was ready for the US to open an office in Pyongyang, he told reporters: "I think it is something that is worth welcoming."
Liaison offices are below the level of embassies but would be a key initial step in normalising relations between the former wartime foes.
Mr Trump and Mr Kim dove into the details of nuclear negotiations Thursday against a backdrop of swirling questions about what Kim was willing to give up and what Trump may demand in the face of rising domestic turmoil.
Tempering expectations, Trump opened by declaring he was in "no rush. We just want to do the right deal."
The two men continued offering hopeful words as talks began anew at their second summit on curbing Pyongyang's pursuit of nuclear weapons, a problem that has bedeviled generations of leaders.
In a sharp break from his rhetoric a year ago, when he painted the threat from Pyongyang as so grave that "fire and fury" may need to be rained down on North Korea, Trump made clear he was willing to accept a slower timetable for denuclearization.
Meanwhile, South Korean President Moon Jae-in plans to offer new proposals for inter-Korean engagement following the high-stakes nuclear summit between the two leaders.
Mr Moon's announcement is planned for a ceremony on Friday marking the 100th anniversary of a 1919 uprising by Koreans against Japan's colonial rule and will likely include plans for economic cooperation between the rival Koreas.
Mr Moon is desperate for a breakthrough in nuclear negotiations between Washington and Pyongyang so he can continue engagement with North Korea. He has driven the three-way diplomacy but is now held back by tough US-led sanctions against the North.