"Some have called the Korean War the 'forgotten war.' But today, we prove these heroes were never forgotten", Vice President Mike Pence said at the ceremony at Hawaii's Joint-base Pearl Harbor-Hickam.
"The remains received from North Korea are being handled with the utmost care and respect by professional historians, forensic scientists, uniformed personnel and government officials", the U.S. -led U.N. Command said in a statement.
"I don't have any announcement today but it's natural to get a lot of business done. but we are not there for any announcements", the official said.
The pledge to return the remains of USA soldiers was made during a landmark summit between the leaders in June in Singapore, where North Korea committed to work towards the complete denuclearisation of the Korean peninsula. They set the caskets gently on risers lined up inside the hangar as Mr Pence stood watching with his hand over his heart.
Sixteen other United Nations member countries fought alongside US service members on behalf of South Korea.
North and South Korea held military talks to build trust yesterday, while the United States detected renewed activity at a North Korean missile factory.
The Defense POW/MIA Accounting Agency will take the remains to a lab on the base where forensic anthropologists will study bones and teeth to identify their race, gender and age.
Last Friday, North Korea returned what were said to be dozens of remains of American soldiers missing from the 1950-53 Korean War, something Kim promised during his summit with Trump.
Friday's transfer of the remains coincided with the 65th anniversary of the 1953 armistice that ended fighting between North Korean and Chinese forces and South Korean and US -led forces under the U.N. Command.More news: Trump to Sessions: end Russian Federation probe 'right now'
The official declined to comment on US spy satellite material that has detected renewed activity at the North Korean factory that produced the country's first intercontinental ballistic missiles (ICBMs) capable of reaching the United States.
"They dedicated their lives for the last 60 years finding out what happened to their fathers, what happened though those patriots, warriors who went to fight for us, for every generation of Americans", Hegseth continued.
North Korea halted nuclear and missile tests, shut down its nuclear testing site and began dismantling facilities at its rocket launch site. "They have missing, France has missing, Americans have - there's a whole lot of us", Mattis added, referencing the fact that service members from other nations in the UN coalition that fought in the Korean War are unaccounted for.
During the summit, the Korean Central News Agency, North Korea's state-run propaganda outlet, claimed that Kim invited Trump to visit Pyongyang at a "convenient time" and that Trump had invited Kim to the US. North Korea also committed to work towards the complete denuclearisation of the Korean peninsula. He said last week that the return was a positive step but not a guarantee that the bones are American.
Identifying the remains will be a challenge.
Appearing before the Senate Foreign Relation Committee in late July, Pompeo acknowledged that North Korean factories "continue to produce fissile material" used in making nuclear weapons.
The Korean War ended in an armistice, not a peace treaty.
Indonesian officials led by Coordinating Human Development and Cultural Affairs Minister Puan Maharani visited North Korea this week, meeting with Kim Yong Nam, the nominal head of state and president of the Presidium of the Supreme People's Assembly.