U.S. chief nuclear negotiator Christopher Hill said Friday that he held "substantive" negotiations on nuclear issues with officials of the Democratic People's Republic of Korea (DPRK) during his three-day visit to Pyongyang.

"The meeting (with DPRK officials) were indeed very lengthy, indeed very substantive," Hill, who returned from DPRK earlier on the day, said after meeting with his South Korean counterpart Kim Sook in Seoul.

"There's been a lot of problems in the past couple of months regarding the six-party process, so we had a substantial review of activities," Hill said at a news briefing.

However, he refused to disclose more details about his visit to DPRK, saying he should first report to the U.S. government and other nations involved in the six-party talks on the nuclear issues on the Korean Peninsula, including China, Japan, Russia and South Korea.

Hill said that during his visit to Pyongyang, he held a series of talks with DPRK officials, including his DPRK counterpart Kim Gye-kwan and Lt. Gen. Li Chan-bok, the chief military representative assigned to the truce village of Panmunjom.

Hill went to Pyongyang on Wednesday and originally scheduled to return to Seoul on Thursday. He extended his visit by another day and went back to Seoul through Panmunjom on road on Friday.

Following the meeting with Hill, Kim Sook said there was a certain degree of progress made in Hill's trip, adding he and Hill agreed that there should be further consultations on the matter within the framework of the six-party negotiations, possibly in October.

Hill is to travel to Beijing on Saturday to discuss the latest situation on the nuclear issues on the Korean Peninsula with Chinese officials and then leave for Washington.

(Xinhua News Agency October 4, 2008)