Aug 17 (Reuters) - Venezuela is making a last ditch attempt to limit the number of companies that could participate in a court-ordered auction of shares in a parent of oil refiner Citgo Petroleum, appealing to the U.S. Supreme Court to overturn a lower court's ruling. Venezuela's petition is asking the Supreme Court to find the lower court's "alter ego" decision was faulty. It does not affect the case against Venezuela filed by miner Crystallex International, whose $970 million claim led to the proposed auction of shares. The petition seeks to have briefs filed by September 15 - just ahead of the start of the proposed auction. A Delaware court judge has set Oct. 23 as the start date for the auction.

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Persons: Nicolas Maduro, Gary McWilliams, Deepa Babington, David Gregorio Our Organizations: Petroleum, U.S, Supreme, ConocoPhillips, Exxon Mobil, Tenaris SA, CITGO Petroleum Corporation, Venezuela, Crystallex, Thomson Locations: Venezuela, PDV, United States, Illinois , Louisiana, Texas, Delaware, Houston, PDVSA