President Moon Jae-in said Wednesday that inter-Korean relations and efforts to restart talks on ending the North's nuclear ambitions are still in a critical condition, despite his agreement to hold a summit with the North's reclusive leader Kim Jong-un next month.

"We have now come to a very critical juncture in our efforts to establish peace and denuclearize the Korean Peninsula," the president said in a meeting with the leaders of five major political parties at his office Cheong Wa Dae.

The remarks came one day after Moon's five special envoys announced their agreement with Pyongyang to hold a summit between the leaders of the two Koreas in late April. The inter-Korean summit, the third of its kind, is scheduled to be held at a South Korean facility located just south of the inter-Korean border, making Kim the first North Korean leader to step on South Korean soil since the end of the 1950-53 Korean War.

The agreement was reached during the envoys' two-day trip from Monday to the communist state where they also held unprecedented talks and a dinner with the North Korean leader.

Moon expressed hope for resumption of dialogue between the US and the North, which he earlier called a prerequisite to resuming multilateral negotiations aimed at ridding the North of nuclear weapons.

The South Korean envoys, headed by Moon's top security adviser Chung Eui-yong, earlier said the North Korean leader expressed his country's willingness to talk with US, also quoting Kim as saying his country is willing to put the denuclearization issue on the table as well.

US President Donald Trump apparently welcomed the outcome of the inter-Korean talks, saying he believed the North's proposal to talk was "sincere."

Pyongyang has also agreed to suspend all military provocations, including nuclear tests and ballistic missile launches, as long as US-North Korea dialogue is in progress.

The North staged 10 ballistic missile launches since Moon took office in May 2017. It also conducted its sixth and most powerful nuclear test so far in September.

Moon remained cautious.

"I believe it is still too early to be optimistic because we are only at the starting line," Moon told the party leaders, according to Cheong Wa Dae pool reports.

The party leaders included Choo Mi-ae of the ruling Democratic Party and Hong Joon-pyo of the main opposition Liberty Korea Party. The rest were Yoo Seong-min of the minor opposition Bareunmirae Party, Cho Bae-sook of the Party for Democracy and Peace, and Lee Jeong-mi of the progressive Justice Party.

It marked Moon's third meeting with party leaders since coming into office, but the first involving the head of the main opposition party, who had boycotted the first two meetings, which were held last year.

Hong earlier asked the president to limit the topics of Wednesday's meeting to security and inter-Korean issues, which the president accepted.(Yonhap)