Clear differences of opinion are emerging between South Korea and the US over how to deal with North Korea, with the US accusing Pyongyang of attempting to “buy time” to further advance its nuclear weapons and ballistic missile programmes.

Washington’s firm position has been underlined by Marc Knapper, the acting US ambassador at the embassy in Seoul, who on Wednesday said that Pyongyang should demonstrate its willingness to talk by dropping its insistence that its nuclear weapons are not open to negotiation.

“We have seen enough times the North used dialogue with us and South Korea and others to continue to buy time to pursue nuclear and missile developments”, Mr Knapper said.

That position was reiterated by Heather Nauert, a spokeswoman for the State Department in Washington, who told reporters on Tuesday, “Our policy is denuclearisation. Our policy has not changed.

“We have talked about this policy since day one of this administration. And that’s maximum pressure, but it’s also the denuclearisation of the Korean Peninsula”, she added.