North Korea has abruptly cancelled UN Secretary General Ban Ki-moon's visit one day before he was due to arrive.
Mr Ban was due to visit an industrial complex in the Kaesong economic zone run jointly by the North and South.
Speaking at a forum in Seoul, he said the move was "deeply regrettable" and that no explanation was given.
He would have been the first UN chief to visit North Korea in more than 20 years. Mr Ban said he wanted to promote reconciliation.
When he first announced the meeting on Tuesday, he said he would "urge North Korea to co-operate with the international community for the Korean Peninsula and for peace and stability", reported Yonhap.
Mr Ban, who was previously South Korea's foreign minister, was due to meet South Korean business leaders and North Korean workers on his trip to Kaesong.
The two countries remain technically at war as the 1950s Korean War ended with an armistice, not a peace treaty.