Sung Kim, the U.S. ambassador to the Philippines, heads out in a vehicle from the Four Seasons Hotel in downtown Seoul on July 2 after meeting with North Korean officials. (Yonhap/EPA-EFE/Shutterstock)

Sung Kim, the U.S. ambassador to the Philippines, held talks with North Korean officials in the demilitarized zone between the two Koreas over the weekend, the State Department said Monday, amid skepticism of the country’s denuclearization efforts.

The meeting appears to be the first face-to-face contact between U.S. officials and their North Korean counterparts since President Trump met with leader Kim Jong Un on June 12 in Singapore.

The State Department announced later Monday that Secretary of State Mike Pompeo will again visit Pyongyang on July 5-7 to “to continue consultations” with North Korean officials. Pompeo will also travel to Tokyo, Hanoi, Abu Dhabi and Brussels for the NATO summit next week.

Pompeo, who has taken a leading role in negotiations with North Korea, has said it may take years to implement an agreement that would eliminate the nation’s nuclear stockpile. 

Sung Kim, an ambassador to South Korea from 2011 to 2014 and a nuclear negotiator with the North during previous talks, has taken on a key role in dialogue with Pyongyang in recent months. In late May, the envoy led a meeting between U.S. officials and North Korean officials, also in the demilitarized zone, ahead of the Singapore summit.

The State Department said in a statement that Kim had led a delegation that met with North Korean counterparts Sunday in the village of Panmunjom, where they discussed the next steps toward implementing the joint declaration signed by Trump and Kim Jong Un last month.

“Our goal remains the final, fully verified denuclearization of the DPRK, as agreed to by Chairman Kim in Singapore,” the statement said, referring to North Korea by the initials of its official name, the Democratic People’s Republic of Korea.

The meeting comes amid growing scrutiny of Pyongyang’s commitment to denuclearization and as joint efforts to repatriate the remains of U.S. troops from North Korea are taking longer than many anticipated. 

The Washington Post reported Saturday that U.S. intelligence officials have evidence showing that North Korea does not intend to give up its entire nuclear weapons stockpile, despite Trump’s claim that there is “no longer a nuclear threat” from the country after the Singapore summit.

Speaking on CBS’s “Face the Nation” on Sunday, White House national security adviser John Bolton said that Pompeo would be “discussing this with the North Koreans in the near future about really how to dismantle all of their WMD [weapons of mass destruction] and ballistic missile programs in a year.”

According to reports in South Korea, Sung Kim met with North Korean Vice Foreign Minister Choe Son Hui at Panmunjom for an hour and a half Sunday. The reports, citing an unidentified diplomatic source, said that Andrew Kim, head of the CIA’s Korea Mission Center, delivered a letter from Pompeo to Kim Yong Chol, North Korea’s main envoy in talks.

Asked about the U.S. diplomat’s visit, Kim Eui-keum, a spokesman for South Korea’s presidential Blue House, said Seoul was aware of the meeting but that it would be inappropriate to comment further. Sung Kim was later photographed leaving the Four Seasons hotel in Seoul early Monday.

Van Jackson, a former Pentagon official who teaches at Victoria University of Wellington in New Zealand, said the presence of a respected diplomat such as Sung Kim could level the playing field during negotiations with North Korea. He added that Pompeo was using the “best folks he can find in the bureaucracy.”

However, Jackson said, Kim’s involvement with what he saw as a disappointing summit in Singapore showed the limits of this approach. “It doesn’t matter how savvy of a diplomat you are,” Jackson said. “If there’s an irreducible conflict of interests between two parties, there’s just not space for diplomatic maneuvers.”

Min Joo Kim contributed to this report.