Kim Yong Chol, considered the North Korean leader's right-hand man, is the most senior official from Pyongyang to visit the United States in 18 years.

Pyongyang's envoy joined Pompeo at the apartment of a US diplomat on Manhattan's East side on Wednesday for talks over an evening meal that lasted about an hour and a half. Two more meetings are scheduled for Thursday.

"Good working dinner with Kim Yong Chol in New York tonight," Pompeo tweeted. "Steak, corn, and cheese on the menu."

It was the third meeting between the two officials who are working to finalize planning for a June 12 summit designed to end a nuclear standoff that has threatened to plunge Korea back into war.

"They are meeting to see what needs to be done in the two weeks that remain," a senior US official said.

"Between now and if we're going to have a summit, they're going to have to make clear what they're willing to do."

US and North Korean envoys have also been meeting in Panmunjom in the Demilitarized Zone between North and South Korea, and an American team is in Singapore to make logistical arrangements for the meeting.

Washington wants North Korea to quickly give up all its nuclear weapons in a verifiable way in return for sanctions and economic relief.

But analysts say North Korea will be unwilling to cede its nuclear deterrent unless it is given security guarantees that the US will not try to topple the regime.

- Russia urges caution -

Meanwhile, Russia's foreign minister, who arrived in Pyongyang on Thursday for talks with Kim Jong Un, warned against setting expectations too high and urged all sides to "avoid the temptation to demand 'everything and now.'"

"We believe it is very important to treat these contacts in a very delicate manner, not to make any abrupt movements, to artificially speed up the process that requires a significant amount of time," Lavrov said, according to a transcript released by the Russian foreign ministry.

"We call on all involved sides to fully appreciate their responsibility for not allowing this very important but still fragile process to break down," he said, adding that Russia was ready to contribute to ongoing diplomatic efforts.

Photos and video released by Russian state media showed Kim and Lavrov, who was making his first visit to the North since 2009, shaking hands.

Lavrov passed on greetings from President Vladimir Putin to Kim and invited him to visit Russia, the Russian foreign ministry said.

Russia is the latest major nation to reach out to North Korea since Trump accepted Kim's proposal for a summit to defuse tensions. Kim has already had two meetings each with Chinese leader Xi Jinping, South Korean President Moon Jae-in, and Pompeo -- once as CIA director and then as secretary of state.

Lavrov spoke with Pompeo by telephone for the first time Wednesday, ahead of his Pyongyang trip.

Earlier this month, President Donald Trump suddenly announced a cancellation of the summit, before reversing course 24 hours later.

- Frenetic meetings -

Pompeo has scheduled a news conference on Thursday, at the end of his meetings with Kim.

The recently-appointed secretary of state called his South Korean and Singaporean counterparts over the weekend, and Japan is also keenly watching summit preparations.

Kim Yong Chol, who is making his first US visit, is the most senior North Korean on US soil since Vice Marshal Jo Myong Rok met then-president Bill Clinton in 2000.

The general has played a key role during recent rounds of diplomacy aimed at ending the nuclear stalemate on the Korean peninsula.

He sat near to Trump's daughter Ivanka during February's closing ceremony for the Winter Olympics in South Korea, an event that was seen as a turning point in the nuclear crisis.

He also accompanied Kim Jong Un on both of his recent trips to China to meet President Xi Jinping, and held talks with Pompeo in Pyongyang.

The key task ahead of the June 12 summit is to settle the agenda. The main stumbling block is likely to be the concept of "denuclearization" -- both sides say they are in favor of it, but there is a yawning gap between their definitions.

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