A statement by North Korea’s foreign ministry said “if confidence is to be built between North Korea and the US, it is essential to conclude a peace treaty for terminating the state of war, a root cause of the hostile relations to begin with”.

Washington has been attempting to persuade Pyongyang to return to the negotiating table and take part in Six-Nation talks on ending North Korea’s nuclear programme. Pyongyang withdrew from the talks in April 2009 after the US tightened sanctions against North Korea, in retaliation for the North’s nuclear tests and missile launches.

Robert King, the new US envoy on human rights in North Korea, said bilateral ties could only improve if Pyongyang improved its appalling human rights record.