Top U.S. diplomats yesterday said they expected China to enforce sanctions unanimously passed by the U.N. Security Council to curtail North Korea’s pursuit of nuclear weapons. In an appearance on CBS’ “Face the Nation,” Secretary of State Condoleezza Rice said China, which shares an 880-mile border with North Korea and is Pyongyang’s principal trading partner, would shoulder the major responsibility of stopping trade with the isolated communist state. Without China’s cooperation on enforcement, sanctions likely would be ineffective. Full Story