US Secretary of State Mike Pompeo hailed "progress" in talks with North Korean leader Kim Jong Un in Pyongyang Sunday before landing in Seoul on a whirlwind diplomatic visit to the region.
The top US diplomat met with Kim for around two hours Sunday morning in the North's capital, where denuclearisation and a second US-North Korean summit were expected to be high on the agenda, before the pair shared a lunch together.
"Had a good trip to Pyongyang to meet with Chairman Kim," Pompeo tweeted. "We continue to make progress on agreements made at Singapore Summit. Thanks for hosting me and my team."
The visit was Pompeo's fourth to North Korea. US President Donald Trump met Kim in Singapore in June for the first-ever summit between the countries.
Speaking to Pompeo via an interpreter following the morning's talks, Kim praised their "nice meeting".
He added: "It's a very nice day that promises a good future ... for both countries."
After a previous visit to Pyongyang in July, Pompeo had said the two foes had made progress on key issues. But within hours of the Secretary of State departing the North released a statement condemning "gangster-like" demands from the US, raising questions over how much the two sides really saw eye to eye.
An official on Sunday's latest visit to Pyongyang with Pompeo said the trip was "better than the last time", but added: "It's going to be a long haul."
Details of Sunday's discussions were not immediately available. But prior to the meeting, Pompeo tweeted that he would "continue our work to fulfil the commitments made (by) POTUS and Chairman Kim," using an acronym to refer to US President Donald Trump.
On the flight to Tokyo, Pompeo said his aim was to "develop sufficient trust" between Washington and Pyongyang to inch towards peace.
"Then we are also going to set up the next summit," said Pompeo.
However, he played down expectations for a breakthrough.
"I doubt we will get it nailed but begin to develop options for both location and timing for when Chairman Kim will meet with the president again. Maybe we will get further than that," said the top US diplomat.
No sitting US president has ever visited North Korea, which according to human rights groups remains one of the most repressive countries on Earth.
Since the Singapore summit, which yielded what critics charge was only a vague commitment by Kim towards denuclearisation of the Korean peninsula, the road towards warmer ties has been bumpy.
Trump scrapped a previously planned trip by his top diplomat to Pyongyang after what he said was insufficient progress towards implementing the terms of the Singapore declaration.
But the unorthodox US president has also since declared himself "in love" with Kim.
Washington and Pyongyang have sparred over the exact terms of their vaguely-worded agreement in Singapore, with the US pushing to maintain sanctions and pressure against the North until its "final, fully verified denuclearisation.
Last month the North's foreign minister told the United Nations there was "no way" his country would disarm first as long as tough US sanctions remain against his country.
Analysts say Washington may now consider new options as China, Russia and South Korea seek to relax sanctions.
"North Korea took some steps towards denuclearisation and the US will face criticism from the international community if it continues to demand complete denuclearisation without any lifting of sanctions," said Yang Moo-jin, a professor at the University of North Korean Studies in Seoul.
"We can't rule out the possibility that Washington... may move in the direction of partial easing of sanctions based on progress in denuclearisation," he said.
Speaking alongside Japanese Prime Minister Shinzo Abe earlier in the trip, Pompeo said the two historic allies would have a "fully coordinated, unified view of how to proceed, which will be what is needed if we are going to be successful on denuclearising North Korea."
Pompeo landed Sunday afternoon in South Korea, whose dovish president Moon Jae-in has served as a go-between for the two sides.
South Korean Foreign Minister Kang Kyung-wha has given a hint of what a grand bargain between the two countries could look like.
In an interview with the Washington Post, she said the North could agree to dismantle Yongbyon, its signature nuclear site.
In exchange, the United States would declare a formal end to the 1950-53 Korean War -- which concluded with an armistice rather than a peace treaty -- but North Korea would stop short of delivering an exhaustive list of its nuclear facilities, she said.
After Seoul, Pompeo ends his trip Monday in China, North Korea's political and economic lifeline.
The Beijing stop could be tense as it comes days after Vice President Mike Pence delivered a blistering speech accusing China of military aggression, commercial theft, rising human rights violations and electoral intervention against Trump.