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

The pair agreed to restart working-level dialogue during an impromptu meeting at the Demilitarised Zone dividing North and South Korea in June, but those talks have yet to begin.

"We are willing to sit face-to-face with the US around late September at a time and place that we can agree on," said Choe Son Hui, the North's vice foreign minister in a statement carried by the official Korean Central News Agency.

Choe repeated Pyongyang's call for the US to come up with an "acceptable calculation" or risk jeopardising the entire diplomatic process.

North Korea has carried out a series of weapons tests since late July in protest at joint military exercises between Seoul and the US.

Pyongyang has also threatened to pull out of talks with Washington and has blasted senior US officials in recent months.

Kim and Trump adopted a vaguely-worded statement on the "complete denuclearisation of the Korean peninsula" at their first summit in Singapore in June last year but little progress has since been made on dismantling the North's nuclear programme.