New York's main contract, West Texas Intermediate light sweet crude for delivery in August, fell 24 cents to $106.08 a barrel, while Brent North Sea crude for August retreated 31 cents to $108.78.

Focus is on Bernanke's views on the US economy and monetary policy Wednesday and Thursday, with dealers hoping for more clues about the future of the Fed's huge bond-buying scheme

"Markets are in particular looking for further signs of whether the central bank has plans to start scaling back on stimulus in later half of this year," Phillip Futures said in a market commentary.

Singapore's United Overseas Bank said "markets most likely will.... stay cautious" ahead Bernanke's appearance.

The United States is the world's biggest oil consuming nation and the health of its economy is a key influence on crude prices.

Bernanke has said Fed will maintain its growth-oriented policies "for the foreseeable future" but some analysts expect the $85 billion-a-month stimulus programme to be wound down from the end of the year.