U.N. Secretary-General’s upcoming trip to North Korea was cancelled when his invitation was withdrawn.

U.N. Secretary-General Ban Ki-moon said Wednesday that North Korea had withdrawn an invitation to visit a factory park in the country, the last major cooperation project between the rivals.

Ban had planned to visit the Kaesong industrial park just north of the heavily fortified Korean border on Thursday in part of his efforts to help improve ties between the rivals. The park is jointly run by North and South Korea.

He would have been the first U.N. chief to visit the factory park, which opened in 2004 in the town of Kaesong. He would also have been the first head of the U.N. to visit North Korea since Boutros Boutros-Ghali traveled there in 1993.

Ban told a forum on Wednesday that North Korea had informed the U.N. that it was reversing its decision to allow him to visit the park.

He described Pyongyang’s decision as “deeply regrettable,” saying no explanation was given for the last-minute change.

Ban said 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.

Ban’s cancelled trip comes relations between the Koreas remain strained following the North’s continuation of missile and other weapon tests that South Korea views as provocations. There are also worries about North Korea after South Korea’s spy agency said last week that North Korean leader Kim Jong Un had his defense chief executed by anti-aircraft gun fire in late April.

The park opened during a period of warming ties between the Koreas and has been considered a test case for unification, pairing cheap local labor with South Korean know-how and technology.

[wpResize]