New York's main contract, light sweet crude for delivery in September, fell 45 cents to $96.95 per barrel.

Brent North Sea crude for September delivery shed 15 cents to $117.28.

A drawn-out political impasse in the United States as polarised politicians struggled to find a mutually agreeable middle ground over a debt solution for the world's largest oil consumer was exacting its toll on traders.

"Prices remain largely range-bound... as a result of the economic uncertainty, particularly with regard to the US budget impasse," said Sanjeev Gupta, who heads the Asia-Pacific oil and gas practice at Ernst & Young.

Congress was due later Thursday to consider Republican Speaker John Boehner's plan to raise Washington's $14.3 trillion debt ceiling although it looked doomed to fail due to a White House veto threat.

US lawmakers were privately hunting for a compromise to avert a debt default due to kick in on August 2.

Copyright AFP (Agence France-Presse), 2011