Pyongyang told U.N. officials early Wednesday morning that it had canceled his trip to its border town of Gaeseong, Ban said at a forum in Seoul.

“No explanation was given for this last-minute change. … This decision by Pyongyang is deeply regrettable,” he said, adding that the notification was delivered via “diplomatic channels.”

“However, as the secretary-general of the United Nations, I will not spare any efforts for peace on the Korean Peninsula and beyond,” he said.

Later in the afternoon, Pyongyang lashed out at the U.N. that its Security Council is being controlled by Washington, in an apparent move to justify its sudden cancellation of Ban’s visit.

North Korea has been under heavy sanctions by the Security Council for three nuclear tests in 2006, 2009 and 2013 and multiple missile launches. Ban also said on Tuesday that North Korea’s nuclear development and other forms of provocations are a clear violation of the U.N. Security Council resolution.

In Seoul, the former South Korean foreign minister met with President Park Geun-hye for talks on current inter-Korean tensions and ways for peace.

The U.N. chief said a day earlier that he would visit the joint industrial complex to encourage North Korean workers there and also to bring the message of peace to the reclusive regime.

He would have been the first U.N. chief to visit the factory complex, a showcase of cooperation between the South and the North. He also would have been the first U.N. chief to visit North Korea in 22 years since Boutros Boutros-Ghali in 1993.

Ban’s announcement surprised many in and out of the country. Especially South Koreans, as it came amid growing tension between the two Koreas, despite Seoul’s repeated offer of talks.

Prospects for a thaw in inter-Korean ties plummeted rapidly with Pyongyang’s recent test of a ballistic missile from a submarine and the live-fire drill in the western maritime border last week. North Korean leader Kim Jong-un’s alleged public execution of his top aides also intensified concerns over his reign of terror.

The Seoul government also expressed regrets over Pyongyang’s sudden withdrawal of Ban’s visit and urged the regime to come forward to improve strained ties with South Korea and also with the international community.

“We regret to hear that North Korea had canceled U.N. chief Ban’s visit to Gaeseong which was being pushed for peace on the Korean Peninsula and to make progress in (the regional) security and in inter-Korean ties,” said an official at the Unification Ministry, adding that Seoul was not informed by Pyongyang of its decision.

Pyongyang’s last-minute cancellation -- an explicit diplomatic discourtesy to the chief of the world’s largest international organization -- may have come from a sense of urgency that it needs to reorganize internal affairs first after the purge of Kim’s defense chief Hyon Yong-chol late last month, according to experts here.

“The decision could have been made by Kim reflecting his desire to tighten his grip first after the purge of Hyon. … It also reflects that North Korea has little capacity right now to deal with foreign affairs,” said Yoo Ho-yeol, a North Korean studies professor at Korea University in Seoul.

“They must have approved the plan in the beginning to use Ban’s trip as a tool to improve North’s image and to promote its propaganda. But things are different now,” he said.

Yang Moo-jin, professor at the University of North Korean Studies also said it appears to be “a safe decision” for North Korea as the regime feels insecure about Ban’s visit.

“North Korean officials may feel pressured about Ban’s visit because they fear how his visit would affect their workers there … and they don’t want to upset Kim,” he said.

By Cho Chung-un (christory@heraldcorp.com)