US President Joe Biden’s administration says it has been trying to contact the North Korean government since February to prevent tensions escalating but has received no response.
North Korean state media has yet to acknowledge that Biden is now the US president.
Washington and Pyongyang remain at loggerheads over North Korea’s missile programmes.
Three meetings between former president Donald Trump and North Korea’s Kim Jong-un, although superficially cordial, achieved little of a lasting nature as they failed to persuade North Korea to give up nuclear weapons – a key demand of the US and other Western powers.
A US official told Reuters there have been “multiple attempts” to engage with North Korea but there has been no meaningful contact for more than 12 months, which includes much of Trump’s final year as president.
Trump’s second summit with Kim, in Hanoi, Vietnam, ended with Trump offering Kim a lift home on presidential jet Air Force One instead of his planned lengthy train journey through China. Kim declined.
Biden has called Kim a thug and stressed the need for North Korean nuclear disarmament before heavy US and UN economic sanctions can be eased.
He has already announced a policy review of North Korea, which is expected to be unveiled in April.
Relations between the US and North Korea plummeted in 2017 when North Korea tested long-range missiles capable of hitting American cities.
While calling on the US to ditch its “hostile policies” the North Korean leader has continued to emphasise his country’s military capability, claiming the development of more accurate long-range missiles, super large warheads, spy satellites and a nuclear-powered submarine, all announced for his birthday in January.
North Korea’s nuclear ambitions are expected to feature prominently during this week’s visit to Japan and South Korea by US Secretary of State Anthony Blinken and Defence Secretary Lloyd Austin.
North Korea is currently more cut off from the outside world than ever before. Its borders have been closed for over a year to prevent the spread of Covid-19 and trade with its main ally China has dwindled by more than 90% in the last few months.