China called on South and North Korea Monday to continue to work together to improve ties, despite Pyongyang\'s recent move to indefinitely delay planned reunions of families separated by the 1950-53 Korean War. North Korea on Saturday abruptly canceled the scheduled reunions, which would have been the first in nearly three years, accusing Seoul of what it calls a \"hostile\" stance toward Pyongyang. South Korea has urged the North to reconsider the decision, calling it \"very regrettable.\"    Asked about the North\'s latest move, China\'s foreign ministry spokesman Hong Lei told reporters, \"We have seen relevant reports. The improvement of inter-Korean relations and the achievement of reconciliation and cooperation serve the common interests of both sides.\"    \"There have been a relaxation of tensions on the Korean Peninsula,\" Hong said during a regular press briefing. \"This situation is a hard one.\"    the ministry spokesman said, \"The relevant momentum of dialogue can be kept up. The two sides should work to improve their relations so as to move the situation on the Korean Peninsula in a favorable direction.\"    Millions of families remain separated following the Korean Peninula\'s division in 1945 and the ensuing three-year conflict. The North\'s cancellation of the planned unions is posing a new challenge to a reconciliatory mood, following heightened tensions earlier this year triggered by Pyongyang\'s third nuclear test. Analysts in Seoul believe that North Korea is using the issue of family reunions to press the South to resume the long-suspended tours to the North\'s mountain resort of Kumgang on its east coast.