Washington has "done nothing for the implementing the joint statement" from the first US-North Korea summit held in Singapore last year, Kim Kye Gwan, advisor to North Korea's foreign ministry, wrote in a statement carried in Pyongyang's official news wire KCNA.

The official then slammed Washington for its joint military drills with the South, which it has long considered rehearsals for invasion.

He also claimed while Pyongyang has made "sincere efforts to build trust", US politicians remain "obsessed" with the idea of enforcing sanctions until Pyongyang completely gives up its nukes first.

"This makes me doubt whether a new breakthrough could be brought about in the DPRK-U.S. relations though another DPRK-U.S. summit talks may open," Kim Kye Gwan said in the statement, using North Korea's official name.

But the official praised US President Trump as "different from his predecessors", adding he would like to "place hope" on Trump's "wise option and bold decision" for the future dialogues between the two countries.

"I and the DPRK Foreign Ministry will follow the future moves of the U.S.," he said.

The North's statement came two weeks after Trump fired the hawkish former national security advisor John Bolton, and said he would consider trying a "new method" in talks with Pyongyang.

Trump had criticised Bolton's suggestion of the "Libyan model" for North Korea, a reference to a denuclearisation deal with the African nation's former dictator Moamer Kadhafi -- who was killed after being deposed in 2011.

Pyongyang had bristled at that comment, which Trump said had "set us very back very badly".

The North has described Bolton as "a nasty trouble-maker" and a "human defect" in the past and hailed his exit.

Negotiations between Pyongyang and Washington have been gridlocked since a second summit between Kim and Trump in February ended without a deal.

The two agreed to restart working-level dialogue during an impromptu meeting at the Demilitarized Zone dividing the two Koreas in June, and Pyongyang has offered to hold those talks in late September, a move the US has described as "encouraging".

There has been no announcement yet on the venue and precise schedule for the talks.