US President Donald Trump has sent a letter to North Koran leader Kim Jong-un, an informed familiar with the ongoing denuclearization talks between Washington and Pyongyang told CNN.

It was flown to Pyongyang and delivered by hand, the source said on Monday night.

The letter comes as the two sides negotiate details of a second meeting between the two leaders.

According to the source, North Korea's former intelligence chief Kim Yong Chol -- one of Pyongyang's top negotiators -- could visit Washington to finalise details of the upcoming summit.

CNN had previously reported that US scouting teams visited Bangkok, Hanoi and Hawaii as they search for a location for the second summit.

Last week, South Korean President Moon Jae-in threw his support behind another Trump-Kim meeting, saying it would be a turning point "that will firmly solidify peace on the Korean Peninsula".

During his visit to Beijing last week, Kim said that Pyongyang will make efforts for the second summit with the US leader to achieve results that will be welcomed by the international community.

North Korea will continue sticking to the stance of denuclearization and resolving the Korean Peninsula issue through dialogue and consultation, he added.

Trump and Kim held a historic summit last June in Singapore where they had agreed to work towards denuclearization in return for security guarantees from Washington.

Talks are currently stalled due to the lack of a clear disarmament road map.

IANS