Seoul has been examining nine cases of potential imports of North Korean coal, which would breach a resolution passed last August by the U.N. Security Council to choke off funding for Pyongyang's nuclear and ballistic missile programs.
Bolton, in an interview on Fox News, said U.S. Secretary of State Mike Pompeo was prepared to return to North Korea for another meeting with Kim. Notably, the statement didn't directly criticize Trump.
North Korea accused the United States on Thursday of pushing for worldwide sanctions despite goodwill moves by Pyongyang and said progress on denuclearization promises could not be expected if Washington continues to follow an "outdated acting script".
Iranian President Hassan Rouhani told North Korea's foreign minister that the United States can not be trusted, Tehran's state media said, as the United States seeks a deal to rein in the North's nuclear and missile programmes.
"They called for collaboration in forcing sanctions and pressure upon us even at the global meetings". North Korea also accused unidentified high-level USA officials of "going against the intention of President Trump" by "making baseless allegations against us and making desperate attempts at intensifying the global sanctions and pressure".
"They made public the North Korea Sanctions and Enforcement Actions Advisory; and additional sanctions".
The unidentified spokesperson also warned that there is no guarantee that the hard-won atmosphere of stability on the Korean Peninsula will continue.
On Wednesday, U.S. Ambassador to the United Nations Nikki Haley said the United States was "not willing to wait for too long" for North Korea to take steps toward denuclearising.More news: Saudi Arabia Threatens Canadian 9/11, Shows Limits of Twitter Diplomacy
North Korea's foreign ministry said on Thursday it had stopped missile and nuclear tests and dismantled "the nuclear test ground", yet the United States still insisted on "denuclearisation first".
North Korea has condemned the United States for placing fresh sanctions on it and called on the country to respond to its efforts to improve bilateral ties.
North Korean officials have toured China to discuss economic development and speculators are snapping up property along their common border.
The president has also repeatedly defended Kim's intentions, tweeting last month that he was "confident" the leader would "honor the contract we signed &, even more importantly, our handshake".
In the meantime, both Koreas are seeking an end of the Korean War.
North Korea nevertheless went ahead with the return of the remains of USA soldiers killed in the 1950-53 Korean war, it said.
South and North Korea technically remain at war as the Korean War ended only with the armistice treaty.
Earlier on Thursday, North Korea's Rodong Sinmun said in a commentary that ending the Korean War is "the first process for ensuring peace and security not only in the Korean peninsula but also in the region and the world".