WASHINGTON/SEOUL (BLOOMBERG, REUTERS, AFP) - North Korean leader Kim Jong Un received a personal letter from United States President Donald Trump and will put serious thought into its content, North Korea's state-run news agency KCNA said.

In a report published early on Sunday (June 23) in Asia, KCNA did not give details on the letter, but said Mr Kim described it as "of excellent content".

"Kim Jong Un said that he would seriously contemplate the interesting content," the report said.

The front page of the North's official Rodong Sinmun newspaper carried a photo of Mr Kim holding Mr Trump's letter with both hands as he read it in his office.

White House officials did not immediately respond to a request for comment.

But South Korea's presidential Blue House said it was aware of the correspondence through its communication with Washington.

"The government views it as positive in that the momentum of dialogue between the North and the US is being maintained through top-level letter exchanges," the Blue House said.

US-North Korea talks have been stalled since a failed summit in February between Mr Trump and the North Korean leader in Hanoi, Vietnam.

A US official said on Wednesday that the US had no preconditions for new talks, but that progress would require meaningful and verifiable North Korean steps to abandon its nuclear weapons programme.

Mr Trump is due to visit South Korea for meetings with South Korean President Moon Jae-in after taking part in the Group of 20 meetings in Japan this week.

The correspondence emerged as China's President Xi Jinping told Mr Kim that the world wanted him to make progress in nuclear talks with the US, underscoring Beijing's key role in negotiations.

The Chinese President said during a landmark visit to Pyongyang last Thursday that he was willing to play a "positive and constructive role" towards achieving the denuclearisation of the Korean peninsula, the official Xinhua news agency said.

Analysts say the North's apparently friendly overtures to Mr Trump signalled that Pyongyang was ready to break the deadlock with Washington after Mr Kim's summit with Mr Xi.

"China holds the key to what North Korea wants the most - security guarantee and economic development," said Professor Koh Yu-hwan of Dongguk University in Seoul.

"After getting China's promise that it will actively help on these two issues, Kim is reaching out to the US," Prof Koh told AFP.

Mr Xi travelled to North Korea a week ahead of a planned meeting with Mr Trump on the sidelines the G-20 summit in Japan, in what's shaping up to be a possible turning point in the trade war between the world's two largest economies.

China's role as North Korea's vital trading partner and sole security backer gives Mr Xi leverage in his talks with Mr Trump.

US efforts to eliminate North Korea's nuclear arsenal have made little progress since Mr Trump and Mr Kim reached an agreement at their historic Singapore summit last year.

In February, Mr Trump rejected Mr Kim's offer to close some nuclear facilities in exchange for the elimination of the most severe United Nations sanctions on North Korea.

The second Trump-Kim summit ended abruptly in Hanoi.