US President Donald Trump said talks with North Korea in New York have been very positive and he is expecting the delegation from Pyongyang to travel to Washington on Friday to deliver a letter to him from leader Kim Jong Un, The Business Times reported.

"I look forward to seeing what's in the letter," Mr Trump said on Thursday as he left Joint Base Andrews for a trip to Houston. Asked if a deal was taking shape, Mr Trump said: "I think it will be very positive ... The meetings have been very positive."

If the North Korean delegation goes to the White House, it would be the first visit there by high-level officials from there since 2000 when Jo Myong Rok, a marshal, met President Bill Clinton.