S. Korea's Moon seeks nuclear agreement with Kim at summit

South Korean President Moon Jae-in is in Pyongyang for his third summit with Kim Jong Un this year

South Korean President Moon Jae-in and the North's leader Kim Jong Un opened a new round of talks at a summit in Pyongyang on Wednesday with the North Korean nuclear arsenal high on the agenda, but Seoul warned they may not reach an agreement.

Moon is on a three-day trip to the North Korean capital for his third summit with Kim this year, hoping to reboot stalled denuclearisation talks between his hosts and the United States.

After the high symbolism of the two Korean leaders' first meeting in April in the Demilitarized Zone that divides the peninsula, and Kim's historic summit with US President Donald Trump in Singapore in June, pressure is mounting for more substantive progress.

In Singapore, Kim declared his backing for the denuclearisation of the peninsula, but no details were agreed and Washington and Pyongyang have since sparred over what that means and how it will be achieved.

Washington 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.

Asked if any deal on denuclearisation had been struck, Moon's spokesman Yoon Young-chan said: "It's difficult to say at this moment that the two leaders have reached any agreement."

They had "frank and sincere" discussions after Moon arrived in Pyongyang on Tuesday, Yoon told reporters in Seoul, adding: "They still need a lot more talks."

"If and when" they reach an agreement, they would announce it jointly but not take questions, he said.

Wednesday's talks took place at the Paekhwawon official guesthouse on the outskirts of Pyongyang. The two leaders were shown on television walking down a long corridor talking together, followed by their wives, before entering a room where the cameras could not follow.