Update: Seemingly right on cue, the Washington Post has arrived to pour cold water all over Pompeo's insistence that the behind-the-scenes talks are making solid progress. As WaPo points out, the initial one-on-one meeting between Kim and Trump is expected to be more theater than substantive negotiation, and that the two sides are likely already gearing up for a second summit, possibly in the US.

The decision by Trump and Kim to begin their Singapore summit without their top advisers or nuclear arms specialists in the room underscores that their real goal here is to develop a personal rapport and stage a global spectacle rather than to ink the technical details of a denuclearization accord. Both nations have sought to lower expectations for an immediate breakthrough this week in Singapore. Trump has described Tuesday’s summit as the first step in what could be a lengthy process, dangling the possibility of inviting Kim to the United States for a second meeting. And in an indication that Kim is like-minded, North Korean state media described a process of normalizing relations with the United States that would unfold over time. When Trump meets Kim on Tuesday, the two leaders plan to shake hands and take a ceremonial walk before cameras at the Capella Hotel on the tropical resort island here of Sentosa, according to a senior U.S. official. After they hold an hour or two of private discussions accompanied only by their interpreters, Trump and Kim will be joined by their top advisers for a more traditional bilateral meeting.

Meanwhile, the paper reported that the behind-the-scenes talks that Pompeo referred to earlier have made little progress.

The working-level sessions, including those led by Secretary of State Mike Pompeo, have foundered repeatedly over basic issues of what the summit should be about and an inability to close fundamental gaps in understanding over North Korean denuclearization. [...] "They can’t even get past first base on the security assurances because the North Koreans will never define what it actually means to end the hostile policy," said Cha, who was considered by Trump to be ambassador to South Korea. Leading Monday’s talks in Singapore were veteran U.S. diplomat Sung Kim and North Korea’s Choe Son Hui, a vice foreign minister with a long history of dealing with the United States. They were still trying to draft a joint statement outlining the areas of agreement for Trump and Kim. Typically, such precooked statements, or communiques, are worked out far in advance of summits. U.S. negotiators have been unable to get the North Koreans to offer a substantive pledge on denuclearization up front, which has been the chief demand of the Trump administration.

The bottom line: Don't expect a final agreement to materialize this week.

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During a press briefing Monday in Singapore, Secretary of State Mike Pompeo assured reporters who were present that talks between the North Korean and US delegations in Singapore have progressed "rapidly" ahead of the historic summit between President Trump and Kim Jong Un, with Pompeo adding that the talks were still taking place.

"Our ambassador to the Philippines Sung Kim met today with [North Korean] Vice Foreign Minister Choe Son Hui," Pompeo told reporters at a press conference. "They are moving quite rapidly and we anticipate they will come to their logical conclusion even more quickly than we anticipated," he said.

Meanwhile, the Washington Examiner reported that members of the US and North Korean delegations met for a few hours at the Ritz Carlton hotel to discuss the terms of denuclearization.

"North Korea has previously confirmed to us its willingness to denuclearize, and we are eager to see if its words prove sincere," Pompeo said. He added that he is hopeful the summit "will have set the conditions for future productive talks" between Washington and Pyongyang.

The summit has provided "an unprecedented opportunity to change the trajectory of our relationship and bring peace and prosperity" to North Korea, Pompeo said. However, he played down the possibility of a quick breakthrough and added that the summit should set the framework for "the hard work that will follow."

While reporters lobbed questions at Pompeo, he declined to provide any details about what Trump might offer Kim during their meeting - though he said the "US is prepared to take actions that will provide North Korea with sufficient certainty that they can be comfortable that denuclearization doesn't end badly for them."

He also emphasized that the negotiations would NOT be conducted in the open "with the media."

"We are not going to conduct these negotiations in the open with the media," Pompeo said, before adding that "unique steps can be taken" to satisfy the Kim regime without providing sanctions relief. "The ultimate objective we seek from diplomacy with North Korea has not changed," Pompeo said, adding that "complete, verifiable, and irreversible denuclearization of the Korea peninsula is the only outcome that the United States will accept."

In parting, he made it very clear that US sanctions will remain in place as long as the North hasn't denuclearized completely, and that if talks don't move in the right direction, the sanctions "will increase."

Watch Pompeo's full briefing below: