Oil prices edged down on Wednesday as investors awaited the release of US crude stockpiles data for clues about demand in the world\'s biggest economy, analysts said. Brent North Sea crude for delivery in September shed 36 cents to stand at $107.78 a barrel in London midday deals. New York\'s main contract, West Texas Intermediate (WTI) for August, dipped 22 cents to $105.80 a barrel. The US Department of Energy will on publish its weekly energy inventories report on Wednesday. During the previous two weeks, crude stockpiles in the United States plummeted by almost 20 million barrels, much more than analysts had expected. The market was waiting also for the start of Federal Reserve chief Ben Bernanke\'s testimony to Congress on the US economy and monetary policy. Bernanke will give his semi-annual testimony over two days in Washington, with investors eager for clues about the Fed\'s view of the US economy and its plans on when to taper its $85 billion-a-month bond-buying scheme. Analysts at JBC Energy research group said \"traders are now focusing on the upcoming... inventory data release as well as Fed Chairman Bernanke\'s testimony, both due later today\".