NY -- Standard&Poor's CreditWire 12/18/98 -- Standard&Poor's long-term ratings on British Petroleum Co. PLC and related entities remain on CreditWatch with positive implications (see list below). Standard&Poor's long-term ratings on Amoco Corp. and related entities remain on CreditWatch with negative implications (see list below). Standard&Poor's also affirmed its 'A-1'-plus commercial paper rating on each company. Upon completion of the merger and clearance by the U.S. Federal Trade Commission, and provided that there are no significant changes in the business and operating profiles of the companies in the interim, Standard&Poor's will assign its double-'A'-plus corporate credit rating and its 'A-1'-plus commercial paper rating to the combined entity (BP Amoco Plc). Standard