“The optimistic would say that [North Korean leader Kim Jong-un] needs it for a domestic audience so he can change his ways and have a new approach; the pessimist would say it’s another way to split the allies apart.”

While saying that the current mood of detente and negotiation had given hope for a process “moving forward towards a lasting peace” on the Korean peninsula, Eyre said the North Koreans were “experts at separating allies”.

“So what could an end-of-war declaration mean? Even if there is no legal basis for it, emotionally people would start to question the presence and the continued existence of the United Nations Command,” he said. “And it’s a slippery slope then to question the presence of US forces on the peninsula.”

Eyre spoke as US secretary of state Mike Pompeo headed for his fourth visit this year to North Korea, seeking to break an impasse in denuclearisation talks and clear the way for a second summit between Kim and US President Donald Trump. Pompeo is due in Pyongyang on Sunday after a stop in Japan, where he met Prime Minister Shinzo Abe to make sure the two allies were on the same page.

Pompeo told Abe it is important for him to hear from the Japanese leader “so we have a fully coordinated and unified view” to successfully denuclearise North Korea.

North Korea had long sought a formal end to the Korean war to replace the armistice that stopped the fighting but left it and the US-led UN Command still technically at war.

At a June 12 summit between Trump and Kim in Singapore, the US leader pledged security guarantees for North Korea if it abandoned nuclear weapons that potentially threaten the United States.

Trump has said he wants “at some point” to bring back US troops from Korea.

South Korean President Moon Jae-in is seeking an end-of-war declaration by the end of the year, arguing it would encourage North Korea to denuclearise. Washington has argued that Pyongyang must give up its nuclear weapons first.

Additional reporting by Associated Press