An active-duty Venezuelan army colonel who is a military doctor has dropped his allegiance to President Nicolas Maduro, backing opposition leader Juan Guaido instead."Ninety percent of us in the armed forces are really unhappy," said Colonel Ruben Paz Jimenez said in a video released on Saturday. "We are being used to keep them in power."He urged his fellow soldiers to help allow humanitarian aid into Venezuela. The shipment of US aid is currently in Cucuta, Colombia, on the border.Maduro has vowed to prevent the aid from entering, labeling it a precursor of a US invasion.A week ago, Air Force General Francisco Yanez also dropped his allegiance to Maduro. The military's backing is critical to the sway of power in Venezuela.Venezuela's self-proclaimed acting president Guaido on Friday refused to rule out the possibility of authorizing United States intervention to help force President Nicolas Maduro from power and alleviate a humanitarian crisis.The opposition leader launched a bid to oust Maduro last month, declaring himself interim president, a move recognised by the US and around 50 other countries, including 20 from the European Union.Under Maduro's stewardship, oil-rich Venezuela's economy has collapsed leaving the country wracked by hyperinflation, recession and shortages of basic necessities such as food and medicine.Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.