Benchmark West Texas Intermediate crude for September delivery fell 36 cents to close at US$107.10 a barrel on the New York Mercantile Exchange. The contract had risen US$4.06, or four per cent, over the previous six trading sessions.
Brent North Sea crude, the benchmark for international crudes, fell 50 cents to US$109.90 a barrel for October delivery on the ICE Futures exchange in London.
Political turmoil in Egypt has supported higher oil prices. The country has been racked by ongoing clashes between supporters of ousted president Mohammed Morsi and the military-backed government. Nearly 900 people have died in the violence so far.
Egypt is not a major oil exporter, but there is concern that an escalation in fighting could spread to neighbouring countries or disrupt the Suez Canal, a major trade route.
Traders are also waiting for clear signals from the U.S. Federal Reserve on monetary policy. It is widely held that the Fed will begin to reduce its $85 billion a month in asset purchases as early as September.
The Fed's stimulus policy has lowered interest rates and made oil and other commodities a more attractive investment by offering potentially higher returns.
In other energy futures trading on the Nymex, heating oil fell one1 cent to US$3.07 a U.S. gallon (3.79 litres), wholesale gasoline fell three cents to US$2.93 a gallon and natural gas rose 10 cents to US$3.46 per 1,000 cubic feet.
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