LONDON: Oil prices slipped on Friday and were on track for a third consecutive weekly decline, pressured by muted demand in China and hopes of a Gaza ceasefire deal that could ease Middle East tensions and accompanying supply concerns. Brent crude futures for September dipped 56 cents to $81.81 a barrel by 2:50 p.m. Saudi time. US West Texas Intermediate crude for September fell 40 cents to $77.88. For the week, Brent is trading down almost 1 percent while WTI is down more than 2 percent.