Venezuela's Guaido challenging Maduro through humanitarian aid

Boosted by the backing of 20 European Union countries, Venezuela's opposition warned the military on Tuesday not to prevent humanitarian aid from entering the country as parliament leader Juan Guaido stepped up his challenge to President Nicolas Maduro's authority.The opposition-dominated National Assembly warned the military, the power behind Maduro, not to cross the "red line" by blocking aid.Maduro, though, claims humanitarian aid would be the forerunner of a US-led invasion.