Cuba on Thursday accused the United States of secretly moving special forces closer to Venezuela as part of a plan to intervene in the country’s political crisis. Cuba, an ally of Venezuela’s president, Nicholas Maduro, alleges that the U.S. was using the pretext of a humanitarian crisis in order to move in on the South American country. President Trump has been trying to pressure Maduro to step down and hand over power to opposition leader Juan Guaido. Cuba said Thursday that the U.S. wanted to “forcibly establish a humanitarian corridor under international protection, invoking the obligation to protect civilians and applying all necessary measures.”

Cuba has been a key backer of Maduro since the Bolivarian Revolution began under former leader Hugo Chavez in 1998. Most Western countries, including the United States, recognize Guaido as Venezuela’s legitimate head of state and pledged humanitarian aid in support, according to Reuters. However, getting that aid across Venezuela’s border with Colombia and Brazil is difficult due to the government’s objections.