West Texas Intermediate crude headed for a fifth weekly decline, the longest falling streak in nine months, while investors await a speech from Federal Reserve Chair Janet Yellen. Brent slipped amid adequate supplies. Futures declined 0.4 percent in New York , bringing the weekly loss to 3.9 percent. Traders are watching for signs of the timing of interest-rate increases from Yellen, who speaks today at a Fed symposium in Jackson Hole , Wyoming . A preliminary gauge of Chinese manufacturing missed estimates yesterday, bolstering concerns that demand growth will slow. “The main pressure is because of the oversupply we see in the market,” Hans van Cleef, energy economist at ABN Amro Bank NV in Amsterdam, said by phone. “There’s a lot of cash at the moment that needs to be invested somewhere, perhaps in commodities. If something comes out of the meeting that will hurt the amount of money, […]