TOKYO • US President Donald Trump may have fallen "in love" with North Korean leader Kim Jong Un, but Pyongyang wants more than just beautiful words. It wants Washington to prove its affection - by lifting sanctions.

As Secretary of State Mike Pompeo heads to Pyongyang this weekend to prepare the ground for a second Trump-Kim summit, North Korea appears to have upped its demands, arguing that the United States should prove it is serious about dialogue by easing sanctions, before Pyongyang takes steps to denuclearise.

Mr Pompeo will also travel to Japan, South Korea and China from Oct 6 to 8, and will be in North Korea on Sunday.

"I think it shows forward progress and momentum that the secretary is making his fourth trip back in less than a year," State Department spokesman Heather Nauert told a briefing, referring to the Pyongyang trip. "Of course, we have quite a way to go but we look forward to the next steps in this conversation."

The invitation to Mr Pompeo to return to Pyongyang was made during a meeting with North Korean Foreign Minister Ri Yong Ho on the sidelines of the United Nations General Assembly last week.

After a summit between the leaders of the two Koreas last month, Mr Kim said he was prepared to permanently dismantle his country's main nuclear site, but only if the US also took "corresponding steps" to build trust.

At the time, it appeared that meant a declaration to formally end the 1950-53 Korean War, as a signal that hostilities between the two countries were over. But over the past few days, Pyongyang has signalled it may want more than that.

A declaration to end the war should have come half a century ago, after the warring parties signed an armistice agreement, the Korean Central News Agency wrote in a commentary on Tuesday. "It can never be a bargaining chip for getting the DPRK denuclearised," the KCNA said, referring to North Korea by its formal name, the Democratic People's Republic of Korea.

By contrast, the Yongbyon facility is a "core" part of the country's nuclear programme, KCNA argued. Yongbyon is the site of the country's only nuclear reactor, producing plutonium that can be used in nuclear weapons, but is also believed to house a separate uranium enrichment facility.

"The KCNA commentary shows that North Korea is constantly raising its demands," said Dr Woo Jung-yeop, a researcher at South Korea's Sejong Institute.

A similarly combative message was delivered by Mr Ri at the UN last Saturday. "The perception that sanctions can bring us to our knees is a pipe-dream of those who are ignorant about us. But the problem is that the continued sanctions are deepening our mistrust," he said.

The US argues that the sanctions should remain in place until North Korea has fully denuclearised.

Associate Professor of Political Science Vipin Narang at Massachusetts Institute of Technology said the comments "really put a little bit of cold water" on the hope that North Korea might provide a list of its nuclear and missile sites in return for an end-of-war declaration.

To build trust, North Korea, he said, appears to want "a transformation of the relationship, and the first step of that would have to be comprehensive sanctions relief".

Experts say Pyongyang is not ready to offer a comprehensive list of its nuclear facilities, believing this would either be disbelieved or give the US a list of future military targets.

Instead, it wants to take things at its own pace, offering up Yongbyon as part of a phased process where both sides take steps to build trust.

For now, Mr Pompeo may explore how serious North Korea is in its offer to dismantle Yongbyon, and what it wants in return; and then decide if that represents a sound basis for another meeting between Mr Trump and Mr Kim.

Mr Trump had last Saturday taken his enthusiasm for his detente with Mr Kim to new heights by declaring at a rally with supporters that "we fell in love" after exchanging letters.

Mr Pompeo's trip to China on Monday comes as the two countries are embroiled in an escalating trade war.

Yesterday, Chinese Foreign Ministry spokesman Hua Chunying said that China and the US would exchange views on bilateral ties and regional and international issues of common concern.

WASHINGTON POST, REUTERS