Pyongyang said while it had taken "such practical denuclearization steps as discontinuing nuclear test and ICBM test fire" and "broadminded measures" like the repatriation of US Korean War remains, "the US responded to our expectation by inciting international sanctions and pressure against (North Korea)."
The statement, credited to North Korea's Foreign Ministry, notably did not blame Trump but singled out "some high-level officials within the US administration" who it said were going against the President's will. It also echoed criticism of previous administrations' approaches to North Korea that Trump himself has made.
The statement seems intended to hit a target audience in the US, being released in English by North Korea's mission to the United Nations in New York, rather than just through the state-run Korean Central News Agency, the usual avenue for government announcements.
The statement was also published by KCNA.
Bolton is a longtime Korea hawk and had been a critic of talking with North Korea before Trump opened diplomatic relations. Speaking to CNN on Monday, he said "we're waiting for the North Koreans to begin the process of denuclearization, which they committed to in Singapore and which they've not yet done."
His comments came as US Secretary of State Mike Pompeo, who has been leading negotiations with North Korea and has traveled to Pyongyang multiple times, stressed the process will take time and is still in the early stages.
Ri said Saturday that denuclearization by North Korea should happen "phase by phase," and statement from the foreign minister posted in the media room at the ASEAN forum criticized the US for "raising its voice louder for maintaining the sanctions against (North Korea)."
The frustration expressed by North Korea points to a fundamental disagreement between the two parties as to the timeline and progress of implementing what was agreed by Kim and Trump.
North Korea has made clear it felt the Singapore summit was only a first step, and that its own concessions -- such as freezing nuclear and missile tests and the returning of remains -- should be reciprocated by the US in some manner.
State-run media in North Korea has recently stepped up criticism of the US. An article Thursday in the Rodong Sinmun said a formal peace treaty ending the Korean War must take place before denuclearization.
South Korea's Presidential spokesman Kim Eui-keum said on Monday Seoul is "asking North Korea to speed up its denuclearization" and asking the US to "show sincere efforts about corresponding measures that North Korea is demanding."
One of the goals of North Korea's missile and nuclear program -- which a confidential UN report recently said was still operational -- is to defend itself from US aggression and attempted regime change.
Pyongyang has made clear it views a peace treaty and a security guarantee from the US that Washington will not attack it as a key step in the process towards full denuclearization, and Thursday's statement appeared to express frustration at the lack of progress on these fronts.
"We remain unchanged in our will to uphold the intentions of the top leaders of (North Korea) and the US and to build trust and implement in good faith the (Trump-Kim) joint statement step by step," it said. "The US should, even at this belated time, respond to our sincere efforts in a corresponding manner."