NEW YORK -- A senior North Korean official and the top U.S. diplomat had dinner in New York as President Donald Trump and Kim Jong Un try to salvage prospects for a high-stakes nuclear summit. It's the highest-level official North Korean visit to the United States in 18 years. Kim Yong Chol, the former military intelligence chief and one of the North Korean leader's closest aides, landed midafternoon Wednesday on an Air China flight from Beijing. Associated Press journalists saw the plane taxi down the tarmac before the North's delegation disembarked at JFK International Airport.

During his unusual visit, Kim Yong Chol had dinner for about an hour-and-a-half with Secretary of State Mike Pompeo, who traveled from Washington to see him. The two planned a "day full of meetings" Thursday, the White House said. Their talks will be aimed at determining whether a meeting between Trump and Kim Jong Un, originally scheduled for June 12 but later canceled by Mr. Trump, can be restored, U.S. officials have said.

Before the meeting Pompeo tweeted that he was looking forward to the meeting and was "committed to the complete, verifiable, and irreversible denuclearization of the Korean Peninsula." Later, he tweeted photos of the two meeting, saying he had a "good working dinner with Kim Yong Chol."

Good working dinner with Kim Yong Chol in New York tonight. Steak, corn, and cheese on the menu. pic.twitter.com/1pu4K3oym7 — Secretary Pompeo (@SecPompeo) May 31, 2018

This was Kim and Pompeo's third meeting, but their first meeting in the U.S., reports CBS News' Kylie Atwood.

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The talks come as preparations for the highly anticipated summit in Singapore were barreling forward on both sides of the Pacific Ocean, despite lingering uncertainty about whether it will really occur, and when. As Kim and Pompeo were meeting in New York, other U.S. teams were meeting with North Korean officials in Singapore and in the heavily fortified Korean Demilitarized Zone.

"If it happens, we'll certainly be ready," White House spokeswoman Sarah Huckabee Sanders said of the Singapore summit. Regarding the date for the meeting, she added, "We're going to continue to shoot for June 12th."

North Korean envoy Kim Yong Chol arrives at a hotel in New York, U.S., May 30, 2018. LUCAS JACKSON/REUTERS

North Korea's flurry of diplomatic activity following a torrid run in nuclear weapons and missile tests in 2017 suggests that Kim Jong Un is eager for sanctions relief to build his economy and the international legitimacy the summit with Mr. Trump would provide. But there are lingering doubts on whether Kim will ever fully relinquish his nuclear arsenal, which he may see as his only guarantee of survival in a region surrounded by enemies.

Mr. Trump announced that Kim Yong Chol was coming to New York for talks with Pompeo in a tweet on Tuesday in which he said he had a "great team" working on the summit. That was a shift from last week, when Trump announced in an open letter to Kim Jong Un that he had decided to "terminate" the summit following a provocative statement from the North.

Pompeo, Trump's former CIA chief, has traveled to Pyongyang twice in recent weeks for meetings with Kim Jong Un, and has said there is a "shared understanding" between the two sides about what they hope to achieve in talks. South Korean media speculated that Pompeo could make a third trip to Pyongyang and that Kim Yong Chol was carrying a personal letter from Kim Jong Un and might push to travel to Washington to meet with Trump.

North Korea's mission to the United Nations in New York is its sole diplomatic presence in the United States. That suggests Kim might have chosen to first go to New York because it would make it easier for him to communicate with officials in Pyongyang, North Korea's capital. North Korea and the United States are still technically at war and have no diplomatic ties because the 1950-53 Korean War ended with an armistice, not a peace treaty.

Mr. Trump views a summit as a legacy-defining opportunity to make the nuclear deal that has evaded others, but he pledged to walk away from the meeting if he believed the North wasn't serious about discussing dismantling its nuclear program.

After the North's combative statements, there was debate inside the Trump administration about whether it marked a real turn to belligerence or a feint to see how far Kim Jong Un could push the U.S. in the lead-up to the talks. Mr. Trump had mused that Kim's "attitude" had changed after the North Korean leader's surprise visit to China two weeks ago, suggesting China was pushing Kim away from the table. Mr. Trump's letter, the aides said, was designed to pressure the North on the international stage for appearing to have cold feet.

White House officials maintain that Mr. Trump was hopeful the North was merely negotiating but that he was prepared for the letter to mark the end of the two-month flirtation. Instead, the officials said, it brought both sides to the table with increasing seriousness, as they work through myriad logistical and policy decisions to keep June 12 a viable option for the summit.

Kim Yong Chol is a vice chairman of the North Korean ruling party's central committee. The last official of his stature to visit the United States was Jo Myong Rok, the late first vice chairman of the National Defense Commission, who visited Washington in 2000, South Korea's Unification Ministry said.

The White House emphasized that it has remained in close contact with South Korean and Japanese officials as preparations for the talks continue. Spokeswoman Sarah Huckabee Sanders said Trump will host Japanese Prime Minister Shinzo Abe of Japan on June 7 to coordinate their thinking ahead of the summit. Mr. Trump hosted South Korean President Moon Jae-in last week.

Moon, who has lobbied hard for nuclear negotiations between Mr. Trump and Kim Jong Un, held a surprise meeting with the North Korean leader on Saturday in an effort to keep the summit alive.