A US official said on Sunday that Secretary of State Mike Pompeo`s trip to North Korea was "better than the last time" but further efforts were needed.
The official, who was part of Pompeo`s delegation, indicated some progress was made during the visit, which included a meeting with North Korean leader Kim Jong Un, but added, "It`s going to be a long haul."
US Secretary of State Mike Pompeo had said earlier on Sunday he expected to hold talks with North Korean leader Kim Jong Un that he hopes will lead North Korea to give up a nuclear weapons program that potentially threatens the United States.
Pompeo posted a photograph of himself on Twitter on Sunday waving from the door of his US government aircraft in Tokyo with the caption: "Next stop #Pyongyang to meet with Chairman Kim and continue our work to fulfill the commitments made @potus and Chairman Kim at the #singaporesummit."
Pompeo, who was making his fourth visit to Pyongyang, said on Twitter on Friday he would "continue our efforts to build out a pathway for the denuclearization of (North Korea)."
An official of the State Department was not immediately able to confirm Pompeo`s arrival in Pyongyang, from where outside communication can be limited.
Pompeo visited Tokyo on Saturday and was expected in Seoul later on Sunday. He is also due to visit Beijing before returning to the United States on Monday.
Pompeo said en route to Asia he aimed "to make sure we understand what each side is truly trying to achieve." He said he also hoped to agree a "general date and location" for a second summit between President Donald Trump and Kim following their first meeting in June.
Kim pledged at his June 12 meeting with Trump in Singapore to work toward denuclearization of the Korean peninsula, but his actions since have fallen short of Washington`s demands for irreversible steps to give up its arsenal.
Pompeo declined en route to Asia to give details of his planned negotiations when asked if he would agree to North Korean demands for a declaration to end the 1950-53 Korean War or to South Korea`s suggestion that to break the current stalemate, he should avoid pressing again for an inventory of North Korea`s nuclear weapons.
Trump has appeared keen on a second summit with Kim, even though recent North Korean statements have suggested the two sides are far from narrowing their differences.
Recently, Pompeo has angered North Korea by insisting that international sanctions must remain in place until it gives up its nuclear weapons. On Wednesday, he said there was unanimous support for this at last week`s U.N. General Assembly, even if Russia and China "had some ideas about how we might begin to think about a time when it would be appropriate to reduce them."
Pompeo`s last trip to North Korea did not go well. He left Pyongyang in July hailing progress, only for North Korea to denounce him for making "gangster-like demands." Pompeo did not meet Kim on that trip.
North Korean Foreign Minister Ri Yong Ho told the United Nations last month that continued sanctions were deepening the North`s mistrust of the United States and there was no way Pyongyang would give up its nuclear weapons unilaterally under such circumstances.
In Tokyo, Pompeo met Prime Minister Shinzo Abe and said he would coordinate closely with Japan over talks with North Korea and promised to raise the issue of the abductions of Japanese citizens in his meetings in Pyongyang.