SEOUL (AFP, THE KOREA HERALD/ASIA NEWS NETWORK) - The two leaders of North and South Korea went to the peak of a sacred mountain on Thursday morning (Sept 20), in the last act of South Korean President Moon Jae-in's three-day visit to the North.

In a symbolic first, the first couples of the two Koreas arrived at Cheonji crater lake on top of Mount Baekdu at around 9.20am and took a stroll around the lake.

The 2,744m peak is considered sacred to all Koreans as the birthplace of Dangun, the legendary founder of the first Korean kingdom.

According to Pyongyang's narrative, it is also said to be where Kim Il Sung, the country's founder and Mr Kim Jong Un's grandfather, led his anti-Japanese guerrilla campaign during the 1910-45 colonial rule.

South Korean tourists flock to see the mountain via China but only a handful of Southerners have been granted access from the North Korean side, mostly for research purposes.

"Mount Baekdu is the spiritual mountain for the Korean people and it's the most symbolic mountain," Mr Moon's spokesman told reporters.

The third summit between Mr Moon and Mr Kim Jong Un has given new momentum to Pyongyang's negotiations with Washington.

The North Korean leader on Wednesday agreed to shutter the Tongchang-ri missile-testing site in the presence of international observers, a move the United States welcomed by saying it was ready for immediate talks aimed at denuclearising the North by January 2021.

Pyongyang also said it could dismantle its best-known nuclear facility at Yongbyon, if the US takes "corresponding measures", as North Korean leader Kim Jong Un and South Korean President Moon Jae-in held their third summit this year.

It is an important caveat, but the declaration appeared to break the logjam in nuclear discussions with Washington.

US President Donald Trump welcomed the move, tweeting that Mr Kim had "agreed to allow Nuclear inspections, subject to final negotiations", adding: "Very exciting!"

US Secretary of State Mike Pompeo also praised the "important commitments", saying he spoke with his North Korean counterpart and invited him to meet next week on the sidelines of the United Nations General Assembly.

In Beijing, the Chinese government's top diplomat, Mr Wang Yi, said in a statement carried on the Foreign Ministry's website on Thursday that China strongly supports and warmly welcomes the agreement reached by the two Koreas at their summit in Pyongyang, and believes that the opportunity for peace should not be lost again..

Negotiations had stalled since the historic Singapore summit between Mr Trump and Mr Kim in June, when Mr Kim declared his backing for denuclearisation of the peninsula but no details were agreed.

Washington and Pyongyang have subsequently sparred over what that means and how it will be achieved, with the Trump administration consistently referring to the denuclearisation of North Korea specifically. For its part, Pyongyang has condemned demands for its unilateral disarmament as "gangster-like".

Pompeo said the talks in New York and meetings in Vienna will be the beginning of negotiations on the denuclearisation of North Korea, to be completed by 2021.

Pompeo will chair a Security Council meeting next week on North Korea to discuss US diplomatic efforts that have undergone a major shift in tone from last year.

At last year's UN gathering, President Donald Trump threatened to totally destroy North Korea and derided Kim as "little rocket man".

The Trump administration is facing calls from Russia and China to consider easing tough economic sanctions imposed on North Korea to create an incentive for Pyongyang to move forward.

Experts remain sceptical, pointing out that Pyongyang has already said several times that it has no need for further testing.

Peak diplomacy

Mr Moon and Mr Kim have sought to strengthen the North-South relationship at their Pyongyang summit, agreeing that the North Korean leader will visit Seoul "at an early date".

Mr Moon said the historic trip could happen later this year. It would be the first by a North Korean leader since the Korean War ended in a 1953 armistice, leaving the peninsula divided by the Demilitarised Zone and technically still in a state of war.

The two leaders also agreed to a open permanent facility for family reunions, work towards joining up road and rail links, and bid jointly for the 2032 Olympics.

Video footage showed Mr Moon's motorcade passing through Pyongyang streets on Thursday morning. The streets were lined with crowds in their finest clothes, waving flags and flowers and chanting "Unification of the fatherland!"

Mr Moon and Mr Kim flew separately from Pyongyang's Sunan International Airport to Samjiyon airport near Mount Baekdu, media pool reports said.

Mr Moon arrived in Pyongyang on Tuesday, using his Air Force One plane.

For his trip to Mount Baekdu, however, he was forced to use the smaller Air Force Two as the Samjiyon airport is said to have a short runway that can only land small aircraft.

The two drove from Samjiyon to Mount Baekdu on the Chinese border, a Southern presidential spokesman told journalists.

After the excursion, Mr Moon will fly directly back to Seoul, the spokesman added, ending his three-day visit to the North.