KUALA LUMPUR, Dec 15 (Reuters) - U.S. Secretary of State Antony Blinken has cut short his trip to Southeast Asia due to a COVID-19 case among his travelling party, a State Department official said on Wednesday. The decision was made to mitigate the COVID-19 risk and prioritise health and safety, and Blinken had expressed by phone his deep regret to the foreign minister of Thailand, where he was due to attend meetings on Thursday, State Department spokesperson Ned Price said. The positive case was confirmed on Wednesday while Blinken was in Malaysia. He was in Indonesia the previous two days.