President Trump on Friday hailed the apparent handover by North Korea of the remains of 55 U.S. service members, publicly thanking leader Kim Jong Un for “keeping his word” as the White House tries to maintain momentum on denuclearization talks.

Trump praised Kim during remarks on the South Lawn and announced that Vice President Pence will attend a repatriation ceremony when the remains of the troops killed in the Korean War are transferred to Hawaii next week after being examined at Osan Air Base in South Korea.

“I want to thank Chairman Kim in front of the media for fulfilling a promise that he made to me,” Trump said after a U.S. military plane carrying the remains in coffins landed at the base. “These incredible American heroes will soon lay at rest on sacred American soil.”

The turnover marked the first transfer of U.S. remains from North Korea since 2007, and Defense Secretary Jim Mattis raised the possibility that the Pentagon could deploy military teams to the North for the first time since 2005 to continue to search for fallen U.S. troops. Pence, whose father was a Korean War veteran, said in a statement that he would travel to Hawaii on Wednesday to receive the remains.

Former U.S. government officials cautioned that North Korea’s action — while a positive step for military families that have sought closure for decades — should not be viewed as a sign that Kim’s regime is demonstrating a greater willingness to work toward denuclearization.

“It fits a very familiar pattern of North Korea’s negotiating square-dancing,” said Daniel Russel, who served as a high-ranking Asia policy official in the Obama administration. “You make very vague, very sweeping proclamations and declarations about your willingness to do right by mankind and achieve global denuclearization. Then you move slowly, you try to put the focus on a very small, very concrete issue, and you make it complicated and difficult. The breakthrough then bears no connection to denuclearization and substitutes for progress.”

Trump, who last month became the first sitting U.S. president to meet with a North Korean leader, sought to use the moment to tout progress on his signature foreign policy issue ahead of the midterm elections this fall. A week after the June 12 summit, Trump falsely asserted that North Korea had already turned over the remains of 200 service members.

In his remarks Friday, which came during an appearance before reporters to tout economic progress, the president recalled that during his 2016 campaign he heard from families of Korean War casualties about the importance of bringing the remains of their loved ones home.

“They asked if I could do something about it,” Trump said. “I’d look at them, I’d say, ‘We don’t get along too well with that country.’ They said, ‘Whatever you can do.’ And it’s something that was very important to me.”

The nuclear talks have faltered since the Singapore summit, however, as Pyongyang has lambasted the United States for what it has called the Trump administration’s “unilateral and gangster-like demand for denuclearization.”

Late last week, North Korea appeared to take steps to dismantle a rocket launching facility, according to satellite images, which the White House hailed as evidence of progress. But experts cautioned that the site was of decreasing strategic value to Pyongyang.

Mattis called North Korea’s turnover of the remains a “humanitarian act” that “sets a positive environment and a positive tone for other things.” The Pentagon has not sent military teams to the country to search for remains since 2005, when the George W. Bush administration ended the practice amid security concerns for the U.S. personnel.

The Obama administration never reached an agreement with North Korea to resume the process. The Pentagon has estimated that 7,700 U.S. troops killed in the Korean War remain unaccounted for, including 5,300 north of the 38th parallel, which marks the border between the two Koreas.

“We have families that when they got the telegram have never had closure,” Mattis said, referring to how the U.S. government notified families of those killed in action.

The Pentagon chief added that the remains will be examined in South Korea for “anomalies,” and forensics testing will follow in Hawaii, where the Pentagon maintains a laboratory to test remains thought to be U.S. service members.

Russel, the former Obama aide, said a sign of real progress would come if Pyongyang discloses a list of its nuclear arsenal and begins negotiating over an international inspection and verification process.

“We are not even at the beginning,” Russel said. “We can’t even see the starting line where are today.”