(Reuters) -Oil was headed for a second week of declines even as it rose on Friday, as the dollar firmed before a speech by Federal Reserve Chair Jerome Powell while concerns over tight supply eased. "No doubt the Fed's policy outlook will be the key driving force for markets ahead," said Yeap Jun Rong, market analyst at IG. Investor caution ahead of Powell's remarks at the Jackson Hole Symposium lifted the safe-haven dollar to a 10-week high, its biggest rise in a month, as markets waited for word on how long rates would stay elevated.