UPDATE 1-Norsk Hydro cautious on outlook after weak Q3

* Q3 operating loss of 793 mln crowns, missing all fcasts * Sells automotive structures business to German Benteler * To consider additional restructuring as markets weak (Adds details, comments) OSLO, Oct 27 (Reuters) - Norwegian aluminium producer Norsk Hydro (NHY.OL: Quote, Profile, Research) posted a larger than expected third-quarter loss, hit by low prices, frail global growth and a weak U.S. dollar, and said it remained cautious on the outlook for its business. Norsk Hydro made an underlying operating loss of 793 million Norwegian crowns ($143 million) for the quarter, after a 1.5 billion crown profit a year ago and lagging analysts' average loss forecast of 351 million crowns in a Reuters poll. Forecasts for the world's third-largest integrated aluminium supplier and a major energy producer in Norway ranged from a loss of 20 million to 698 million. "We remain cautious about the outlook for global aluminium demand and are concerned about the weakening U.S. dollar," Chief Executive Officer Svein Richard Brandtzaeg said. "In view of these challenges, we will consider additional restructuring and cost-saving measures," he said. Hydro has seen demand fall sharply as the global economic crisis has weighed on demand for aluminium and in turn prices. Hydro said it was selling its automotive structures business to Germany's Benteler Automobiltechnik GmbH. The transaction is expected to be cash neutral for Hydro, and an estimated after-tax loss of 250 million crowns will be recognized in next quarter's results, Hydro said. (Reporting by Aasa Christine Stoltz, editing by Will Waterman) ($1=5.541 Norwegian Crown)