North Korea should take "concrete" measures in order to resume the long-stalled six-party negotiations on ending the communist country's nuclear weapons program, a senior U.S. envoy said Wednesday. Glyn Davies, the U.S. envoy on North Korean affairs, made the remarks in a meeting with reporters in Seoul after talks with his South Korean counterpart, which was focused on ways to denuclearize the North. "What we need is not just change in attitude, but change in direction, in fact, concrete steps from North Korea," Davies said. "But so far, North Korea has been a no-show on nuclear issues."    "What we are looking for from North Korea is sincerity, its movement, actions, they know what it is they agreed to do back in September of 2005 and what the United Nations Security Council has decided about their nuclear missile activities."    In the landmark 2005 agreement in the six-party denuclearization talks, the North agreed to discard its nuclear program in return for international energy and other aids, but the country has conducted three nuclear bomb tests from 2006-13 in breach of the six-party agreement as well as U.N. resol The multilateral talks involving the two Koreas, the U.S., China, Russia and Japan have been stalled since late 2008 as the North's development of nuclear arms continued. Led by China, the key sponsor of North Korea, the countries involving the forum have been discussing the resumption of the disarmament talks, but Washington and Seoul have shown reservations about an early resumption of the talks, citing North Korea's broken promises. "We will have to make sure North Korea's leadership will change strategic calculation and find that possessing nuclear weapons is not actually in his strategic interest," Cho, the South Korean point man on the North Korean nuclear issue, told reporters in the joint press meeting with Davies following their bilateral discussion. "Our two countries will keep working on a number of initiatives and efforts so that we will be able to have the six-party talks back on solid ground, on which we can expect substantive progress and also we can expect fundamental solutions of the North Korean nuclear issue when the talks are resumed," Cho said. Despite the North's recent proposal to halt the joint annual South Korea-U.S. military drills scheduled to run from late February to April, the two alies will conduct the military exercise as planned, both officials said. "We are going to keep planning and conducting our joint exercise, which is defensive in nature and that which will continue year after year," Cho said. "We will continue on a transparent basis to conduct these defensive exercises so we are ready should any contingencies arise," Davies said. Ahead of the joint annual military drills involving a massive number of South Korean and U.S. soldiers and arms, the North has accused the two allies of conducting a rehearsal of war against North Korea The officials' comments followed recent key political developments in North Korea. The North executed leader Kim Jong-un's once-powerful uncle Jang Song-thaek last month, and it has been engaging in a series of charm offensives toward South Korea, offering family reunions and asking to halt cross-border slander. The shock execution of Jang, who was accused of treason, was widely believed by the outside world as an indication of political instability in North Koea, with young leader Kim at the helm. Dvies also said he briefed Cho on the result of his trip to Beijing, the first leg of his three-nation Northeast Asia trip. Seoul and Washington have been reportedly pressing China, the major sponsor of North Korea, to induce the North to accommodate conditions set forh by South Korea and the U.S. for resuming the six-party talks. Davies' visit is part of back-to-back Asia trips by ranking U.S. foreign affairs officials of late. U.S. Deputy Secretary of State William Burns flew to Seoul last Monday to discuss the denuclearization issue, and his visit was followed by a trip Sunday by assistant secretary of state on Asian affairs, Daniel Russel. These visits will be followed by U.S Secretary of State John Kerry's trip to Seoul and the Asian region, Davies said, confirming the report of Kerry's Asia visit planned for February. Davies is scheduled to depart for Japan on Thursday after holding meetings with other high-ranking South Korean officials including a vice foreign minister.