VIENTIANE, Laos — U.S. Secretary of Defense Lloyd Austin expressed regret Wednesday that his Chinese counterpart chose not to hold talks with him during meetings of Southeast Asian defense chiefs in Laos, calling it a setback for the entire region. The Association of Southeast Asian Nations is holding security talks in Vientiane at a time of increasing maritime disputes with China and as the transition to a new U.S. president approaches. The decision by Chinese Defense Minister Dong Jun “is a