A US military aircraft flew the remains of American servicemen out of North Korea on Friday, a move hailed by the White House as a "positive" step for the fragile detente between the two rivals.
The return of the remains - on the 65th anniversary of the end of the Korean War - marks the partial fulfillment of an agreement reached between US President Donald Trump and North Korean leader Kim Jong Un at their historic summit in Singapore last month.
"After so many years, this will be a great moment for so many families. Thank you to Kim Jong Un," President Trump said in a tweet.
The White House said it was "encouraged" by the return of the remains and the "momentum for positive change".
"Today's actions represent a significant first step to recommence the repatriation of remains from North Korea and to resume field operations in North Korea to search for the estimated 5,300 Americans who have not yet returned home," it said.
After leaving the North Korean port city of Wonsan, the C-17 cargo plane landed at the Osan US Air Base in South Korea at around 0200 GMT, where live TV images showed American soldiers lined up for a ceremony.
The United Nations Command (UNC) in South Korea said 55 sets of remains were on board the plane.
"It was a successful mission following extensive coordination," General Vincent Brooks, commander of the UNC and United States Forces Korea, said in a statement.
"Now, we will prepare to honour our fallen before they continue on their journey home."
More than 35,000 Americans were killed on the Korean Peninsula during the war, out of which around 7,700 are still considered missing, including 5,300 in North Korea alone, according to the Pentagon.
Between 1990 and 2005, 229 sets of remains from the North were repatriated, but those operations were suspended when ties deteriorated over Pyongyang's nuclear weapons programme.
The remains flown to Osan on Friday are expected to be sent to Hawaii for forensic identification, following a formal repatriation ceremony next Wednesday.
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Mr Trump has hailed his summit agreement with Mr Kim as effectively ending the North Korean nuclear threat, although it contained only an ill-defined commitment on Pyongyang's part to the "denuclearisation of the Korean peninsula" - a long way from the complete, verifiable and irreversible disarmament demanded by Washington.
The issue of repatriating remains of American war dead was seen as a far less contentious one, and the summit agreement specified the immediate return of those remains "already identified."
According to US officials, North Korea is estimated to have as many as 200 sets of remains ready for delivery.
Former New Mexico governor Bill Richardson, who has worked on repatriation issues and visited North Korea several times, warned that Pyongyang might hold up further repatriations in order to squeeze some cash out of the United States.
"They'll give a certain amount of remains for free right away," Mr Richardson told the Washington Post. "But then they'll say, 'The next ones, we need to find them, locate them, restore them.' And then they'll start charging, and they'll milk this."
The initial repatriation provides the White House with a tangible result from the Singapore summit, which has otherwise failed to deliver on the denuclearisation expectations raised by the US president.
US Secretary of State Mike Pompeo was despatched to Pyongyang in early July to nail down the North's summit commitments - including returning the remains of US servicemen.
Mr Pompeo described the talks as "constructive" but the North Korean foreign ministry condemned his "gangster-like" demands for rapid nuclear disarmament.