UN Secretary-General Ban Ki-moon said Wednesday, May 20, that North Korea had cancelled an invitation for him to visit a factory park in the country that represents the last major cooperation project between the rival Koreas

Ban had previously said that he wanted to go Thursday to the Kaesong industrial park just north of the heavily fortified Korean border to help improve ties between North and South Korea, which jointly run the complex but have seen always tense ties worsen in recent weeks.

He would have been the first UN chief to visit the factory park, which opened in 2004 and is a rare, legitimate source of foreign currency for the impoverished North, and the first UN head to visit North Korea since Boutros Boutros-Ghali in 1993.

North Korea gave no reason when it told the UN of its decision to cancel his trip, Ban told a forum in Seoul on Wednesday. Analysts had said Ban's trip wouldn't likely bring any major breakthrough in ties between the Koreas, and some have calculated that Pyongyang made a last-minute determination to cancel because it was unlikely to get much out of such a visit.

"This decision by Pyongyang is deeply regrettable," Ban said, adding he will spare no effort to encourage the North to work with the international community for peace and stability on the Korean Peninsula and beyond.

Lim Byeong Cheol, a spokesman for Seoul's Unification Ministry, expressed regret over the North's decision, saying the country must accept offers for dialogue and cooperation by the UN and other members of the international community instead of isolating itself.