President Barack Obama is preparing to block the sale of new offshore drilling rights in much of the U.S. Arctic and parts of the Atlantic, a move that could indefinitely restrict oil production there, according to two people familiar with the decision. Obama will invoke a provision in a 1953 law that gives him wide latitude to withdraw U.S. waters from future oil and gas leasing, said the people who spoke on condition of anonymity because the decision had not been announced.