The US has consulted China over the sinking of a South Korean warship and urged Beijing to play a responsible role amid fresh signs of North Korean involvement, according to Washington's most senior regional envoy. Dr Kurt Campbell, the assistant secretary of state for East Asia and the Pacific, said in Hong Kong last night that Chinese officials had expressed deep concern over the deaths of 46 sailors aboard the Cheonan, a 1,200-tonne South Korean corvette, after an explosion on March 26. Seoul officials now suspect a North Korean torpedo attack - possibly in revenge for a naval clash in November that left a North Korean ship in flames. 'Yes, we've had some consultations and we have explained our role and the seriousness with which we are taking the recovery effort and we've encouraged China to play a responsible role in the time ahead,' Campbell said, when asked whether Washington had raised the issue with Beijing. He refused to elaborate on the possibility of any sanctions or other action if the attack is confirmed, saying the matter was extremely sensitive. The US side was now engaged in the closest possible consultations with its South Korean allies about any future steps. Campbell was speaking after a speech on America's regional engagement to the second International Media Conference, an event organised by the University of Hong Kong and Hawaii's East-West Centre think tank. He also urged action from Beijing not just to resume military exchanges frozen after arms sales to Taiwan but to forge a steadier Sino-US military relationship. The US desired the resumption of military-to-military contacts, he said. It was time to move on from the 'start-stop' talks in the past to more regular military ties. 'We seek to establish a more steady momentum ... we believe that an essential missing element in our high-level dialogue has been this military-to-military component and we believe that they should be resumed in the nearest possible time,' he said. While the overall relationship had broadened and deepened in the past decade, a solid dialogue on military issues had lagged behind, with long-term discussions on strategic nuclear issues falling even further behind. Campbell is the most senior US State Department official to visit Hong Kong since US President Barack Obama took office in January 2008. He will meet government, political and business leaders today before heading to Japan.