Oil prices slip, OPEC doubts weigh ahead of U.S. rig count data

By Ethan Lou NEW YORK (Reuters) - Oil prices fell below $50 on Friday, on track for their biggest weekly loss in six weeks, on doubts about OPEC's planned output cut and ahead of U.S. rig count data that has steadily increased in the last few months. Organization of the Petroleum Exporting Countries experts and counterparts from non-member producers such as Russia started two-day negotiations on Friday in Vienna on limiting output to curb a global glut that has weighed on markets for two years.