North Korean leader Kim Jong-un has received a personal message from US President Donald Trump, expressing his "satisfaction" with "excellent content," the official Korean News Agency reported yesterday, while negotiations between the two countries remain stalled.

"After reading the letter, he said with satisfaction that its content is excellent," the agency said, noting that the North Korean leader "will carefully study its important content, in recognition of President Trump's ability to rule and his exceptional courage."

The front page of the official newspaper Rodong Sinmun published a picture showing Kim in his office reading the letter.

The agency gave no further details on the content of the letter.

The White House announced in a statement that «President Trump sent a letter and there is a correspondence between the two leaders».

"This is a positive thing, as long as the North-US dialogue continues to move forward through the exchange of letters at the highest level," the presidency said.

On June 11, Trump announced that he had received a "wonderful" message from Kim, adding that he still trusted the North Korean leader despite the lack of tangible progress on nuclear disarmament.

The new exchange of letters is "very important," said Professor Yang Mu-jin, a professor at Seoul's North Korean University of Studies.