The White House says President Donald Trump has received a letter from North Korean leader Kim Jong Un, following up on the two leaders' June summit in Singapore.

"A letter to President Trump from Chairman Kim was received on August 1. The ongoing correspondence between the two leaders is aimed at following up on their meeting in Singapore and advancing the commitments made in the US-DPRK (North Korea) joint statement," Press Secretary Sarah Sanders said in a statement.

At the summit, the two sides pledged to work toward toward the denuclearization of the Korean Peninsula. But a document signed by Kim and Trump did not include details of how and when North Korea would denuclearize.

Earlier Thursday, Trump had thanked Kim "for your nice letter," adding that "I look forward to seeing you soon." In the same tweet, the U.S. leader also thanked Kim for transferring presumed remains of soldiers killed in the Korean War

Thank you to Chairman Kim Jong Un for keeping your word & starting the process of sending home the remains of our great and beloved missing fallen! I am not at all surprised that you took this kind action. Also, thank you for your nice letter - l look forward to seeing you soon! — Donald J. Trump (@realDonaldTrump) August 2, 2018

A U.S. Marine stands at attention as caskets conta A U.S. Marine stands at attention as caskets containing the remains of American servicemen from the Korean War handed over by North Korea arrive at Joint Base Pearl Harbor-Hickam in Honolulu, Hawaii, U.S., Aug. 1, 2018. A U.S. Marine stands at attention as caskets containing the remains of American servicemen from the Korean War handed over by North Korea arrive at Joint Base Pearl Harbor-Hickam in Honolulu, Hawaii, U.S., Aug. 1, 2018.

His comments came hours after Vice President Mike Pence presided over a ceremony in the state of Hawaii marking the repatriation of the 55 sets of remains to U.S. soil.

Pence said Trump secured a commitment from Kim during their June summit to return the remains of U.S. service members who were killed in the 1950-53 war. About 7,700 U.S. soldiers are listed as missing from the conflict, and 5,300 of the remains are believed to still be in North Korea.

Vice President Mike Pence (R) receives a flag from Vice President Mike Pence (R) receives a flag from Navy Rear Adm. Jon Kreitz, deputy director of the POW/MIA Accounting Agency during a visit to Joint Base Pearl Harbor-Hickam in Hawaii, Aug. 1, 2018. Vice President Mike Pence (R) receives a flag from Navy Rear Adm. Jon Kreitz, deputy director of the POW/MIA Accounting Agency during a visit to Joint Base Pearl Harbor-Hickam in Hawaii, Aug. 1, 2018.

"Some have called the Korean War the forgotten war," Pence said. "But today we prove these heroes were never forgotten. Today our boys are coming home."

The remains are being sent to Defense POW/MIA Accounting Agency for forensic analysis in order to try to determine their identities.

A U.S. defense official told VOA that North Korea has provided almost no information to help identify the individuals, and that the process could take months or years to complete.

A total of 17 United Nations member countries fought on behalf of South Korea during the war.