Oil slips further below $57 as dollar strength counters OPEC

By Alex Lawler LONDON (Reuters) - Oil slipped further below $57 barrel on Monday as a stronger dollar and ample U.S. supplies outweighed OPEC output curbs and rising tensions between the United States and Iran. U.S. energy companies added oil rigs for a 13th week in 14, data showed on Friday, and U.S. crude inventories rose by more than expected last week. Brent crude was trading at $56.56 a barrel by 1402 GMT, down 25 cents, having touched an intra-day high of $57.13.