U.S. President Donald Trump and North Korean leader Kim Jong Un. AFP

U.S. President Donald Trump on Tuesday in Singapore called North Korean leader Kim Jong Un “very smart” and a “very worthy, very hard negotiator.”

Trump and North Korean leader Kim Jong Un signed a “comprehensive” document, following a historic summit in Singapore aimed at the denuclearisation of the Korean peninsula.

“I learned he’s a very talented man. I also learned that he loves his country very much.”

There were no immediate details on the contents of the document but Trump said he expected the denuclearsation process to start “very, very quickly”.

Before signing what Trump described as a “comprehensive letter”, Kim said the two leaders had a historic meeting “and decided to leave the past behind. The world will see a major change,” he added.

Trump said he had formed a “very special bond” with Kim and that relationship with North Korea would be very different.

“People are going to be very impressed and people are going to be very happy and we are going to take care of a very dangerous problem for the world,” Trump said.

Asked whether he would invite Kim to the White House, Trump said: “Absolutely, I will.”