Benchmark West Texas Intermediate crude for October delivery fell 39 cents to close at US$108.21 a barrel on the New York Mercantile Exchange. For the week, crude was down 1.7 per cent after closing at a two-year high of US$110.53 a barrel the previous Friday.
The price dropped as American and Russian chemical weapons experts huddled in a Geneva hotel to haggle over technical details that will be critical to reaching a deal for securing Syria's chemical weapons arsenal.
Meanwhile, U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov met to examine political developments and plot a new international conference in Geneva to support the creation of a Syrian transitional government.
Syria is not a major oil producer, but oil traders say the possibility of a wider conflict could interrupt production and shipping routes in the Middle East and cause prices to rise.
The November Brent contract, the benchmark for international crudes, rose 17 cents to US$111.70 a barrel on the ICE Futures exchange in London.
In other energy futures trading on Nymex, wholesale gasoline rose one cent to US$2.77 a U.S. gallon (3.79 litres), heating oil was flat at US$3.11 a gallon and natural gas rose four cents to US$3.68 per 1,000 cubic feet.
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