Oil down on strong dollar, OPEC uncertainty

By Libby George LONDON (Reuters) - Oil prices slid on Friday, dragged by a strong dollar and uncertainty over whether OPEC will agree to cut production at the group's meeting next week, but benchmark contracts were on track to close the week with gains close to 4 percent. A strong dollar could crimp fuel demand due to higher costs for holders of other currencies. Reports that state oil giant Saudi Aramco would in January increase oil supplies to some Asian customers also cast a shadow on markets