SEOUL — North Korean officials did not turn up to a Thursday meeting with the U.S. military about repatriating the remains of the war dead, according to a U.S. official with knowledge of the situation.

The two sides had been expected to meet at the Korean Peninsula’s demilitarized zone and discuss the return of U.S. troop remains from the 1950-1953 war — an arrangement the State Department had announced after Secretary of State Mike Pompeo’s visit to Pyongyang Friday and Saturday.

On Thursday, however, Defense Department and United Nations Command officials were left waiting in the DMZ’s Joint Security Area. The expected North Korean officials never arrived, according to the official, who spoke on the condition of anonymity as he was not permitted to talk publicly about the event. 

“We were ready,” the official said. “It just didn’t happen. They didn’t show.”

A State Department spokeswoman declined to comment but noted that Pompeo said after his talks in Pyongyang last week that the date for the meeting remained flexible. Just before departing Pyongyang, Pompeo said that the meeting was set for Thursday but that it “could move by one day or two.”

In a statement released to reporters on Thursday, South Korea’s Foreign Ministry said that North Korean military officials were seeking a meeting with their U.S. counterparts on Sunday.

It was not clear why North Korean officials did not attend the meeting Thursday or whether they had confirmed their intention to.

Ahead of the June 12 summit in Singapore, North Korean officials had failed to attend a planning meeting with their U.S. counterparts, causing tension between the negotiating partners.

The repatriation of the remains of U.S. soldiers from North Korea has been a major issue between Washington and Pyongyang since the end of the Korean War, when thousands of Americans were left in Korea either missing in action or as prisoners of war.

Hundreds of remains have been repatriated since 1990, but the process has been fraught with mistrust. The transfer of remains between North Korea and the United States has not taken place since 2005.

President Trump and North Korean leader Kim Jong Un had pledged to recover more American remains when they met in Singapore to talk about denuclearization. A statement signed by both leaders promised the “immediate repatriation of those already identified.”

Trump told a crowd of supporters a week later that the remains of 200 Americans “have been sent back.” Military officials later denied that but told reporters that they expected the remains to arrive within days and had made prearrangements for their arrival, such as storing caskets at the DMZ.

Since the summit in Singapore, there has been increasing scrutiny of the agreement reached by Trump and Kim, with some experts suggesting that North Korea did not intend to give up its nuclear weapons.

Pompeo visited Pyongyang last week in a bid to ease any misunderstandings between the two parties and find areas where they could make progress. Though the secretary of state described the talks as “productive” after they concluded, North Korea’s Foreign Ministry released a statement that criticized the “regrettable” U.S. negotiating style.

Speaking in Singapore on Thursday, South Korean President Moon Jae-in said that North Korea’s statement was a “strategy that can often be seen in negotiations.” Moon also said that Pompeo’s visit had shown that Pyongyang and Washington had the same view of denuclearization, according to his spokesman Yoon Young-chan.

The South Korean government is “constantly in contact with its U.S. counterpart” about progress of the talks on war-remains repatriation, said Roh Kyu-deok, a spokesman for South Korea’s Foreign Ministry, but it declined to comment on details.

According to estimates from the Pentagon, 7,700 U.S. troops are unaccounted for from the Korean War. Of that number, 5,300 are believed to have been killed north of the 38th parallel, which marks the border between the Koreas. 

Min Joo Kim and Carol Morello in Washington contributed to this report.