Both Seoul and Washington have expressed willingness to talk, but the US President Donald Trump demands the North "denuke" first.
The most senior South Koreans to travel North for more than a decade arrived in Pyongyang on Monday to meet leader Kim Jong Un, the latest step in an Olympics-driven rapprochement on the divided peninsula.
The delegation travelled as envoys of the South's President Moon Jae-in with an aim to push for talks between the nuclear-armed regime and the United States, after Kim sent his sister to the Pyeongchang Winter Games.
"It was agreed... that they would attend a meeting and dinner with Kim Jong Un," said Moon's spokesman.
Both North Korea and the United States have expressed willingness to talk, but US President Donald Trump demands the North "denuke" first.
The North, which has vowed never to give up its nuclear deterrent against US hostility, says it will not sit down to talks under preconditions.
TRT World spoke to journalist Joseph Kim in Seoul.
Reclusive North Korea, which has made no secret of its pursuit of a nuclear-tipped missile capable of reaching the mainland US in defiance of UN Security Council resolutions, is also concerned over a joint US-South Korea military exercise, which it sees as a preparation for war.
South Korean officials have said the drill will start next month as planned, after being postponed for the Winter Olympics held last month in the South.
The 10-member South Korean delegation, headed by National Security Office head Chung Eui-yong, left from Seoul Air Base in Seongnam, near the capital, the official said, on condition of anonymity.
"We will deliver President Moon Jae-in's wish to bring about denuclearisation of the Korean peninsula and permanent peace by extending the goodwill and better inter-Korean relations created by the Pyeongchang Winter Olympics," Chung said at the presidential Blue House before he left.
The delegation hopes to speak with North Korean officials on starting dialogue between the North and the US as well as other countries, he added.
The delegation includes National Intelligence Service chief Suh Hoon and Vice Unification Minister Chun Hae-sung.
The delegation is expected to attend a dinner with North Korean officials on Monday, with another meeting set for early on Tuesday, said another administration official, who sought anonymity because of the sensitivity of the situation.
The delegation will fly to the US on Wednesday to explain the result of the two-day trip to officials in Washington, according to the South's presidential office.
Officials at the Blue House said they were unsure whether or when the North's leader, Kim Jong- un, would meet the delegation.
The government hopes the visit will create "a positive atmosphere," Unification Ministry spokesman Baik Tae-hyun told a regular briefing.
Thawing relations between the neighbours have prompted speculation of future direct talks between Washington and Pyongyang after months of tension and exchanges of bellicose insults between Trump and Kim Jong-un fuelled fears of war.
North Korea has not carried out any weapons tests since late November, when it tested its largest intercontinental ballistic missile. Inter-Korean talks began after Kim Jong-un said in his New Year's address that he wanted to engage the South.
Pyongyang has since sent athletes to participate in the Olympics, as well as a high-ranking delegation that included Kim's sister, Kim Yo-jong.
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.
The North regularly threatens to destroy the South and its main ally, the US, which stations 28,500 troops in the South, a legacy of the Korean War, and carries out regular joint military exercises.
"Neither sanctions nor provocations nor threats can ever undermine our position of a nuclear weapons state," the North's Rodong Sinmun newspaper said recently.
"Hoping that the DPRK would abandon its nuclear programmes is as foolish an act as trying to wish seas to get dried up," it said, referring to itself by its official name, the Democratic People's Republic of Korea.