By Deisy Buitrago and Vivian Sequera CARACAS (Reuters) -Venezuela is prepared for the reimposition of U.S. sanctions on its oil and gas exports and will stop accepting repatriation flights from the U.S. if “economic aggression” intensifies, high-level officials said on Tuesday. The U.S. began reimposing sanctions on Caracas this week after the South American country’s top court upheld a ban blocking the candidacy of the leading opposition hopeful in a presidential election later this year. The Treasury Department on Monday gave U.S. entities until Feb. 13 to wind down transactions with Venezue…