The United States is updating its contingency plans for a possible regime collapse in North Korea and various other scenarios, a top military commander said Thursday. Adm. Samuel Locklear, head of the U.S. Pacific Command (PACOM), said his troops have "detailed planning" for many different types of scenarios of what might unfold on the Korean Peninsula. "And one of those would be a rapidly changing situation that would require stabilization of the peninsula. So that planning is ongoing," he said at a Pentagon news conference. Public anxiety and unpredictability have grown over the future of the North Korean regime, run by a young and untested leader. Kim Jong-un, believed to be in his early 30s, has sent confusing signals on his leadership style. Most recently, his communist regime caught the world by surprise when it purged and executed his uncle Jang Song-thaek, who was seen as No. 2 leader and regent for Kim. The admiral voiced worries about Kim's leadership. His behavior "makes me wonder whether or not he is always in the rational decision-making mode," Locklear said. He described the nuclear-armed North as a "potentially very dangerous place."    The commander in charge of U.S. forces in the Asia-Pacific region made clear that the U.S. will continue annual joint military drills with South Korea as scheduled. "We don't plan to stop the exercises," he said. "We are going to continue to do them as long as the risk on the Korean Peninsula persists."    The North has called for the South and the U.S. to cancel their large-scale military drills scheduled to begin next month on and near the peninsula. On the Pentagon's increased deployment of "rotational" troops and advanced weapons to Korea, Locklear said it is aimed at maximizing the combat readiness of the allies. He dismissed a view that such a move may reflect a change in the U.S. defense strategy on the peninsula. The Pentagon announced a decision to deploy 800 additional Army troops and advanced weapons just south of the border between the two Koreas for nine months from Feb. 1. It also plans to send a dozen F-16 fighter jets to South Korea for a temporary mission. "It got played out like it was a big strategic move, but in reality it was just part of the pre-planned decision we had made in the alliance to make sure we had the most capable forces on the peninsula," Locklear said. Meanwhile, he stressed the need to establish a key military communication channel with China. "I don't have the ability to pick up a phone and talk directly to a PLA navy admiral or general at the time of a crisis. And we need to work on that," he said, using the acronym for the formal name of China's military, the People's Liberation Army. Washington and Beijing are discussing the issue but "things take time," he said. He added he is concerned about the growing risk of conflict between China and Japan, stuck in territorial stand-offs. "Any time you have two large powers, two large economic powers, two large military powers that have a disagreement that they're not talking to each other about that has no clear diplomatic end-state in sight ... the risk calculation can grow," he said.