The neighbours will hold high-level talks next week to prepare for a meeting between the South's President Moon Jae-in and the North's leader Kim Jong Un.
The two sides vowed at that time to work towards North Korea's denuclearisation but have struggled to reach a deal to meet that goal, with the United States insisting that sanctions pressure must be maintained during negotiations.
North Korea said it has halted nuclear and missile tests and dismantled its nuclear test site as practical steps toward denuclearization, but it lashed out at the USA for unilaterally demanding North Korea denuclearize first.
The group, closely following North Korean affairs, said last month the country started dismantling key facilities at the station in the northwestern province.
The White House and US State Department did not immediately respond to requests for comment.
It continued: "Now, the issue in question is that going against the intention of President Trump to advance the DPRK - US relations, some high level officials within the US administration are making baseless allegations against us and making desperate attempts at intensifying the worldwide sanctions and pressure".
"As long as the US denies even the basic decorum for its dialogue partner. one cannot expect any progress in the implementation of the DPRK-US joint statement including the denuclearization", said Pyongyang's foreign ministry, using the initials of the country's official name, warning regional security could suffer.
"The U.S. should, even at this belated time, respond to our honest efforts in a corresponding manner", North Korea added in its statement.
The North apparently wants it to ensure the security of its regime.
But the details of that process remain vague - North Korea did not commit to unilaterally give up its nuclear weapons and the United Nations says its nuclear programme is continuing.
"The idea that we're going to relax the sanctions just on North Korea's say-so, I think, is something that just isn't under consideration", Bolton said.