While a formal peace regime officially ending the Korean War would need buy in from the United States and China - the other participants in the conflict - experts agree that there is nothing to stop the two Koreas declaring an end to the war themselves, or signing a bilateral peace treaty.
North Korean leader Kim Jong Un said Wednesday that he planned to visit Seoul, the South Korean capital, in the "near future", a dramatic diplomatic step that would be a first for Kim. It previously offered to stop nuclear and missile tests but did not allow global inspections for a dismantling of its only known nuclear site in May, drawing criticism that its action could not be verified and could be easily reversed.
Ms Nauert said the United States would "continue to consult very closely and carefully and regularly with the South Koreans" during their meetings in North Korea.
"We are not afraid of future challenges", he said.
But no details were agreed and Washington and Pyongyang have since sparred over what that means and how it will be achieved.
The US is pressing for the North's "final, fully verified denuclearisation", while Pyongyang wants a formal declaration that the 1950-53 Korean War is over and has condemned "gangster-like" demands for it to give up its weapons unilaterally.
North Korea would also shut down its Dongchang-ri missile engine testing and launch facility and allow the process to be monitored by global observers.
Those U.S. steps could include an end-of-war declaration, South Korea's national security adviser, Chung Eui-yong, told reporters.
"These moves are expected to help resolve the worldwide community's doubts toward North Korea's pre-emptive dismantling moves in the past as a mere show", he said, according to a pool report.
North Korea is willing to move towards dismantling its main Yongbyon nuclear site if the United States takes reciprocal actions, the statement said, without providing further details.
"In the meantime there will be no Rocket or Nuclear testing", Trump added.
The Tonchang-ri missile pad is now expected to be closed permanently, but the dismantlement of the Yongbyon nuclear facility will be dependent on USA actions.
Pyongyang has given no indication it is willing to give up its nuclear arsenal unilaterally and is seeking relief from tough global sanctions.
US officials involved in the latest negotiations have said North Korea has refused to even start discussions about defining denuclearization.
Kim's late father, Kim Jong Il, had promised reciprocal visits when South Korean leaders visited him in Pyongyang in 2000 and 2007. But experts said the document only contained vague promises that would do little to curb the North's nuclear program.
In a separate agreement signed by their defense chiefs, the Koreas also agreed to a wide range of steps aimed at further reducing military tension on the Korean Peninsula.
A joint statement also says the two Koreas have agreed to seek to obtain the rights to co-host the 2032 Summer Olympics.
Moon again dangled the carrot of close economic cooperation, promising to reopen a joint industrial complex at Kaesong in North Korea and a tourism center at Mount Kumgang, as well as establish other special economic and tourism zones in the North "as conditions are set".
The two Koreas agreed to begin construction to reconnect railways and roads linking the countries within this year.
The talks have stalled after U.S. President Donald Trump called off a scheduled North Korea trip by his Secretary of State Mike Pompeo, citing what he called a lack of progress in the North's denuclearization process. The meeting will provide an opportunity for Mr Moon to brief the United States president and, more significantly, draw him back to the negotiating table with North Korea.
As the motorcade carrying Moon and Kim to a state guesthouse wove through Pyongyang, huge crowds, mostly women clad in bright flowing dresses, lined the boulevard, waving pink flowers and chanting for reunification.