South Korean President Moon Jae-in was set to embark on a trip to the United States on Sunday for a summit with US President Donald Trump  Moon's trip comes after his visit last week to the communist North where he held his third bilateral summit with leader Kim Jong-un.

Moon will explain the outcome of the latest inter-Korean summit before the entire world when he addresses the United Nations General Assembly. However, his US trip may be more aimed at explaining the summit outcome directly to the US president.

"President Moon is set to thoroughly explain the outcome of the third inter-Korean summit (in 2018) that was held in the interest of the entire world," said Nam Gwan-pyo, a senior director from the presidential National Security Office.

Moon "will hold in-depth discussions (with Trump) on ways to break the impasse in North Korea-US talks and to improve North Korea-US relations," Nam told reporters of South Korean News Agency (Yonhap) earlier. 

The latest Moon-Kim summit marked the third of its kind held since Moon took office in May 2017 and was the fifth inter-Korean summit in history.

Moon's trip to Pyongyang, on September 18-20, came amid a deadlock in denuclearisation talks between the US and the North, partly caused by Trump calling off a scheduled North Korea trip by his Secretary of State Mike Pompeo, citing a lack of progress in the North's denuclearisation process.

In a joint declaration with Moon, Kim agreed to dismantle the North's missile engine test facility and launch pads in Dongchang-ri, which is considered home of the North's newly developed long-range ballistic missiles that can reach the continental US. The North has also offered to dismantle its key nuclear facilities in Yongbyon in exchange for corresponding measures from the US.

Moon said he had additional messages for Trump that come directly from the North Korean leader.