The U.S. special nuclear envoy Wednesday urged North Korea to halt its nuclear and provocative activities, calling on Pyongyang to pursue "authentic and credible" denuclearization.

   Sydney Seiler, Washington's deputy negotiator on North Korea's nuclear issue, listed "representative examples" that the North can show its sincerity toward denuclearization, but he made it clear that the U.S. has no intention to "loosen standards" for the resumption of the long-stalled six-party talks.

   "The (nuclear) programs should not be running. North Korea should refrain from provocative actions. It should move toward a credible path to denuclearization," Seiler told a group of reporters in Seoul. "(But) this is not loosening our standards, certainly not."

   His remarks follow those he made last week in Washington that North Korea could show its commitment to denuclearization by halting its nuclear activities and putting a moratorium on nuclear and missile tests.

   His comments in the U.S. have been viewed by some that the U.S.

may lower its bar for the resumption of the talks as he did not mention halting a highly enriched uranium program as a set of actions for denuclearization.

   Seiler arrived in Seoul on Monday for a three-nation trip that includes stops in China and Japan. His visit to Seoul marked his second since he became the special nuclear envoy in September.

   Earlier in the day, he held talks with his South Korean counterpart, Shin Chae-hyun, to discuss ways to resume the long-stalled six-party talks.

   The six-party talks involving the two Koreas, the U.S., China, Russia and Japan have been stalled since late 2008, when Pyongyang walked away from the negotiating table.

   Since its third nuclear test last year, North Korea has repeatedly expressed its intention to return to the six-party forum "without preconditions." The North also conducted nuclear tests in 2006 and 2009.

   South Korea and the U.S. have said that Pyongyang must first show its sincerity toward denuclearization before such talks can resume. But China, a long-time ally of North Korea, has been urging Seoul and Washington to lower their bar for the talks.

   Seiler said that Pyongyang's dual goal of pursuing nuclear weapons and economic growth cannot be successful, calling on the North to return to the talks and make "authentic and credible" denuclearization.

   "The so-called 'Byongjin' policy, under which it seeks simultaneously to pursue nuclear weapons and economic development, will only succeed once North Korea takes the path of denuclearization," he said.

   Seiler also called for the North to abide by United Nations Security Council resolutions and to honor its 2005 pledge to end its nuclear programs.

   He was referring to the deal adopted at the six-party talks on Sept. 19, 2005, when the North agreed to end its nuclear programs in exchange for aid and security guarantees.

   Meanwhile, the U.S. envoy also called for the North to release two remaining American detainees.

   Last week, North Korea released Jeffrey Fowle, one of three detained American citizens. Kenneth Bae and Matthew Todd Miller are still being kept in captivity.

   "The detention of these Americans has proven to be a roadblock to moving forward a number of bilateral issues," he added.

   Seiler plans to fly to Beijing on Thursday to discuss ways to reopen the six-party forum.

   A flurry of diplomatic efforts is under way among ranking officials from countries involved in the six-party talks.

   Hwang Joon-kook, Seoul's top nuclear envoy, embarked on a five-day trip to China on Tuesday, where he plans to hold talks with his Chinese counterpart, Wu Dawei, in Beijing on Friday.

   The planned meeting between Hwang and Wu will also coincide with the visit by Seiler to the Chinese capital. (Yonhap)