North Korean leader Kim Jong Un has agreed to permanently dismantle his main nuclear complex at Nyongbyon if the United States takes corresponding measures, South Korean president Moon Jae-in said.
It comes after the two leaders held summit talks in Pyongyang to try to sustain nuclear diplomacy with Washington, which has been pushing hard for stronger disarmament moves from the North.
The Korean leaders also said the North would dismantle a missile engine test site and launch pad in the presence of outside inspectors, and would seek to host the 2032 Summer Olympics together.
Mr Moon also said Mr Kim would try to visit Seoul sometime this year.
Washington wants North Korea to outline the entirety of its nuclear programme, and its response to Wednesday's joint statement from the Koreas remains to be seen.
While the declaration appears to fall short of what Washington wants, President Donald Trump has maintained that he and Mr Kim have a solid relationship and both leaders have expressed interest in meeting again after their June summit in Singapore.
But Mr Trump's late-night tweets did not address the US matching North Korea's moves.
"Kim Jong Un has agreed to allow Nuclear inspections, subject to final negotiations, and to permanently dismantle a test site and launch pad in the presence of international experts. In the meantime there will be no Rocket or Nuclear testing," Mr Trump said in a pair of tweets.
"Hero remains to continue being returned home to the United States. Also, North and South Korea will file a joint bid to host the 2032 Olympics. Very exciting!"
'Eliminate danger of war'
North Korea has been demanding a declaration formally ending the Korean War, which was stopped in 1953 by a ceasefire, but neither leader mentioned it as they read the joint statement.
"We have agreed to make the Korean Peninsula a land of peace that is free from nuclear weapons and nuclear threat," Mr Kim said as he stood by Mr Moon's side at the guesthouse where Mr Moon is staying.
"The road to our future will not always be smooth and we may face challenges and trials we can't anticipate. But we aren't afraid of headwinds because our strength will grow as we overcome each trial based on the strength of our nation."
Mr Kim and Mr Moon earlier smiled and chatting as they walked down a hallway and into a meeting room to finalise the joint statement, which also said that the leaders would push for a Korean peninsula without nuclear weapons and to "eliminate all the danger of war".