SEOUL, South Korea (AP) -- South Korea's military began searching for Korean War remains at the heavily armed inter-Korean border on Monday after North Korea ignored its calls to carry out a previously planned joint search.
South Korean soldiers will remove mines and proceed with excavation work at an area south of the military demarcation line that bisects the rivals, said Choi Hyunsoo, spokeswoman for Seoul's Defense Ministry.
The joint recovery of war remains was one of many peace agreements reached between the Koreas last year as they took steps to improve bilateral relations amid larger nuclear negotiations between North Korea and the United States.
But North Korea has shown less enthusiasm about upholding inter-Korean agreements following the collapse of February's high-stakes summit between leader Kim Jong Un and U.S. President Donald Trump over mismatched demands on sanctions relief and disarmament.
The breakdown has been a major setback for South Korean President Moon Jae-in, who held three summits with Kim last year and lobbied hard to revive nuclear negotiations between Washington and Pyongyang following a provocative run in North Korean nuclear and missile tests that led to fears of war on the peninsula.
Moon, who will travel to Washington later this month for a summit with Trump, called for Pyongyang to respond to efforts to keep the atmosphere of dialogue alive and diplomatically resolve the nuclear standoff.
"We surely will not return to the past and cannot return to the past," Moon said in a meeting with senior aides on Monday.
The Koreas had agreed to jointly search for war remains from April 1 to Oct. 31, which was part of a military agreement reached on the sidelines of Moon's third summit with Kim in Pyongyang last September. The North in recent weeks has been unresponsive to South Korean calls for military talks to discuss details about carrying out the search.
"Our side will prepare to immediately switch to a joint search if North Korea later responds," Choi said.
Under the September military agreement aimed at reducing conventional threats, the Koreas also established buffer zones on land and at sea and no-fly zones above their border. They also removed some front-line guard posts and conducted a joint survey of a 70-kilometer (43-mile) -long waterway near their western border under plans to allow civilian vessels from both countries to pass freely.
But Seoul's Defense Ministry said last week that the civilian use of the river estuary will be "postponed" because of the lack of discussions with the North.
The Koreas have also fallen behind on their plans to disarm a jointly controlled area at the border village of Panmunjom and let tourists freely cross concrete slabs forming the demarcation line there. North Korea recently withdrew its entire staff at a frontline liaison office with South Korea before sending some of them back to the office.
Some analysts say North Korea is trying to pressure South Korea into backing its position with the U.S. more strongly. Following the breakdown of the Trump-Kim meeting, North Korean state media have urged the South to distance itself from Washington and resume joint economic projects that have been held back by sanctions.
Experts say the breakdown of the Trump-Kim talks raised further doubts about Moon's claim that Kim is genuinely interested in dealing away his nuclear weapons and about Moon's role as mediator, which has become less crucial with Washington and Pyongyang directly communicating.