Juan Guaido, the leader of Venezuela’s opposition party and the most prominent challenger to current President Nicolas Maduro, will speak with with Vice President Mike Pence on Monday in Bogota, The Associated Press reports Saturday. The meeting comes on the heels of a tense few days in Venezuela: after Maduro attempted to block humanitarian aid at three of the nations’ borders, the military clashed with local residents and killed at least two people, the AP notes. Secretary of State Mike Pompeo condemned the violence in a series of tweets Saturday night, labeling Maduro a “sick tyrant.” The U.S., along with many other nations, has backed Guaido as Venezuela’s rightful leader. “The U.S. condemns the attacks on civilians in #Venezuela perpetrated by Maduro’s thugs,” Pompeo wrote in one post. “What kind of a sick tyrant stops food from getting to hungry people?” he wrote in another. “The images of burning trucks filled with aid are sickening.”