Donald Trump, the US president, has described a personal letter from Kim Jong-un as a “beautiful work of art” and loosened the timeframe on Washington’s demands that the North Korean leader give up his nuclear weapons.

Mr Trump revealed during a meeting in New York on Wednesday with Shinzo Abe, Japan’s prime minister, that he had received an “extraordinary” new letter from Kim, who he plans to meet for a second summit in the near future.

It mirrors an earlier diplomatic overture from Pyongyang, when a senior North Korean official hand delivered a personal message in a giant envelope in June, shortly before the two leaders held their first historic meeting in Singapore.

“He likes me, I like him, we get along. He wrote me two of the most beautiful letters. When I showed one of the letters, just one, to Prime Minister Abe, he said this is actually a ground-breaking letter, this is an incredible, this is a historic letter,” Mr Trump told reporters gathered for the United Nations General Assembly.

“And it is a historic letter, it’s a beautiful, it’s a beautiful piece of art. And I think we’re going to make a deal. Will we make a deal? I don’t really know. I think we’re going to. In the meantime, and I’ve said it, and I don’t want to bore you, no rockets, no missiles, no nuclear tests for over a year,” he added.