UPDATE 2-Venezuela's Guaido orders new boards for PDVSA, Citgo

Venezuelan opposition leader and self-proclaimed president Juan Guaido said on Monday that he has ordered congress to begin the process of naming new boards of directors to state oil company PDVSA and U.S. refining subsidiary Citgo. His advisers are rushing to take control of Citgo, the country's main foreign asset, before a potential bond default that could leave half the company in creditors' hands, sources close to the talks told Reuters earlier on Monday.

Venezuelan President Nicolas Maduro is confronting an unprecedented challenge to his authority after Guaido declared himself interim president last week, citing a fraudulent election. Guaido has won wide international support, including from the United States. On Saturday, Venezuela's top military diplomat in Washington, Colonel Jose Luis Silva, defected from Maduro's government. (Reporting by Corina Pons and Marianna Parraga; Writing by Cynthia Osterman; Editing by Lisa Shumaker and Bill Trott)