Four administration officials clarified to CNN that "planning is underway to receive the remains from North Korea in the coming days, although the actual transfer date and location have not been finalized".
In the joint statement, Kim "reaffirmed his firm and unwavering commitment to complete denuclearization of the Korean Peninsula", but made no reference to a timeline.
The U.S. -based North Korea monitoring group 38 North said in an analysis at the end of last week there had been no sign of any activity toward dismantling Sohae or any other missile test site.
That could allow the lifting of U.N. Security Council economic sanctions that have brought about a plunge in the North's foreign trade, although the USA insists easing of sanctions can only come after Pyongyang shows it has ended its nuclear programs.
"The Chinese people's friendship for the North Korean people will not change, and China's support for socialist North Korea will not change", said Mr Xi. What is know has been pieced together from experts' reports and the North Korean state news agency KCNA.
The last time North Korea turned over remains was in 2007, when Bill Richardson, a former United Nations ambassador and New Mexico governor, secured the return of six sets.
Trump, who has been leading an global drive to press North Korea to abandon development of nuclear missiles capable of reaching the United States, told reporters after the June 12 summit that Kim had pledged to dismantle one of his missile installations.
Jenny Town is a research analyst with 38 North.
6 of 9 North Korean soldiers stand guard at the truce village of Panmunjom at the Demilitarized Zone (DMZ) which separates the two Koreas in Panmunjom, North Korea, Wednesday, June 20, 2018.
"There is no longer a nuclear threat from North Korea".
Trump's meeting with Kim came on the heels of his combative G-7 meeting with traditional US allies, including Canada and the United Kingdom.
However, asked on Wednesday if he could "put his finger on" any steps North Korea had taken to dismantle its nuclear weapons programme, Mattis told reporters at the Pentagon: "No, I'm not aware of that".
North Korea announced before the Singapore summit the suspension of its ICBM testing and also closed its nuclear bomb test site, where it conducted several explosions in front of visiting media that it said were to destroy testing tunnels. The detailed negotiations have not begun. Furthermore, if China and North Korea maintain the current trajectory of diplomatic normalization and economic development, then it will be improbable that sanctions could even be reimposed.
"That's a big thing - for the missiles that they were testing, the site is going to be destroyed very soon".
The site's identification comes just one week after Trump's historic summit with Kim in Singapore, where the two leaders signed a joint statement that said the USA would give Pyongyang unspecified "security guarantees" and Kim would remain committed to "complete denuclearization of the Korean Peninsula".