U.S. presidential candidates and members of Congress demanded more sanctions on North Korea on Wednesday after its latest nuclear test, but major powers will likely be reluctant to take the tough steps necessary to force Pyongyang to abandon its weapons program, former U.S. officials and analysts said.

North Korea is already under a wide array of international sanctions, and diplomats said U.N. Security Council members were expected to discuss the possibility of adding to these in coming days. But the steps taken so far stop short of the all-out economic offensive that forced Iran to the nuclear negotiating table.

Asia analysts said China would likely support more U.N. sanctions, even though it is North Korea's neighbor and main ally, but within limits, for fear of destabilizing what has long been a physical buffer between it and U.S.-backed South Korea.