Foreign ministry spokesman Noh Kyu-duk said, "The government hopes the agreements reached between leaders at the North Korea-U.S. summit, including the repatriation of Korean War remains, will be swiftly carried out as a means to fulfill the objective of complete denuclearization and establishment of a peace system on the Korean Peninsula".
Pompeo has insisted that a raft of tough economic sanctions imposed on North Korea would remain in place until "final, fully verified denuclearization" occurs.
The illegal supplies were provided through ship-to-ship transfers at sea using North Korean tankers that have called in port at least 89 times "likely to deliver" the shipments, according to the report. Under U.N. sanctions, North Korea is allowed to import 500,000 barrels of oil products only and 4 million barrels of crude oil each year.
Earlier Thursday, a diplomatic source here said the USA and North Korea were still in talks to set a date for working-level dialogue over the repatriation of remains of American troops.
What was in Kim's letter?
Attached were two images of the letter - one in Korean and the other an English translation.
Kim expressed deep appreciation for "the energetic and extraordinary efforts made by Your Excellency Mr. President and for the improvement of relations between the two countries and the faithful implementation of the joint statement".
He also says that bilateral trust should be "further strengthened in the future process of taking practical actions". He did not elaborate.
In his letter, which was written 24 days after the June 12 summit in Singapore, Kim addressed Mr Trump as "Your Excellency Mr President".
In return, Washington agreed to halt U.S. military exercises in South Korea. But the president's optimistic outlook about North Korea's willingness to denuclearize and steps in that direction have been brought into question, after an NBC report claiming North Korea has been expanding a nuclear facility.
On Sunday, he brushed off North Korean charges that he used "gangster-like" diplomacy in the negotiations and vowed that he would keep pursuing denuclearization talks with Pyongyang. "Mr. Chairman, it's a great honor to be with you, and I know we'll have tremendous success together and we'll solve a big problem-a big dilemma-that until this point has been unable to be solved, and working together we'll get it taken care of", the president said during the meeting.
It had been expected at the inter-Korean truce village of Panmunjom.
The North, instead, reportedly proposed holding general-level military talks with the United Nations Command (UNC) to discuss returning the war remains to the U.S. It is unknown whether the North Korean side gave any prior notification to the U.S. about this.
Secretary of State Mike Pompeo made his third trip to Pyongyang last week to iron out some of the details of the Singapore statement and described the meetings as "productive".
Trump told a crowd of supporters a week later that the remains of 200 Americans "have been sent back".