North Korean officials have failed to turn up for talks with a US team on the repatriation of the remains of American soldiers killed in the Korean war.
Repatriating remains was a commitment from the 12 June summit between Kim Jong-un and Donald Trump in Singapore .
The talks had been expected in the demilitarised zone on Thursday. Reports say North Korea is now asking for higher-level talks for Sunday.
An estimated 30,000 US soldiers died in the 1950-53 Korean war.
There are about 7,700 US soldiers classified as missing in action from the war.
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In a separate development, the US accused North Korea of violating a UN sanctions cap on refined oil products.
Earlier this year, the UN Security Council limited such exports to North Korea at 500,000 barrels a year.
Thursday’s planned meeting – what happened?
It had been expected at the inter-Korean truce village of Panmunjom.
North Korean and US teams – as well as officials from the UN – had been due to discuss the details of repatriation.
Mr Kim had agreed during the summit with President Trump to recover “POW/MIA remains, including the immediate repatriation of those already identified”. The agreement reportedly covered the remains of some 200 American soldiers.
The US military has since announced that 100 wooden coffins have been moved to the inter-Korean border in preparation.
But North Korea’s delegation failed show up.
Pyongyang has reportedly asked the United Nations Command Armistice Commission to upgrade the talks to a higher level to include a US general, South Korea’s foreign ministry said.
North Korea also proposed to reschedule the meeting for Sunday.
The fact that North Korea seem to be dragging its feet on this issue fuels already growing doubts among President Trump’s critics about whether the Singapore summit was a success or simply a publicity stunt for Mr Kim, the BBC’s Cindy Sui in Seoul reports.
However, South Korea’s President Moon Jae-in said during a visit to Singapore on Thursday that denuclearization talks were on the right track.
He suggested North Korea’s recent complaints and actions were merely negotiation tactics.
There is speculation that North Korea may also want payment for the return of the remains, our correspondent says.
Between 1996 and 2005, some 33 recovery operations were conducted in North Korea which saw 200 sets of remains returned.
However, recovery efforts were suspended when the relationship between both countries worsened, as the North began the advancement of its nuclear programme.