Oil prices fall as focus shifts to U.S. output

By Libby George LONDON (Reuters) - Oil prices slipped on Friday, giving up gains from earlier in the day, as market shifted its focus towards production increases in the United States from efforts by OPEC and other producers to support prices by cutting supplies. Brent crude futures , the international benchmark for oil prices, were trading at $55.55 per barrel at 1050 GMT, down 69 cents from their last close. U.S. West Texas Intermediate (WTI) crude futures were at $53.30 a barrel, down 48 cent