WASHINGTON, July 26 (Reuters) - Vice President Kamala Harris could travel to Vietnam and Singapore in August, even as details of such a trip are not final yet, a source familiar with the matter said on Monday. The coronavirus pandemic is likely to be on Harris" agenda, the source said, speaking on condition of anonymity. Harris recently visited Mexico and Guatemala with the aim of lowering migration from the region. During her trip she focused on issues such as economic development, food insecurity and women"s issues.