Oil dropped in price by $US5 to a three-month low on Friday.
US light crude settled down $US4.82 to $US115.20 a barrel, before falling to $US114.90 in post-settlement trade - its lowest level since early May. London Brent crude settled at $US113.33, down $US4.53.
Prices reached a record high of $US147.27 a barrel on 11 July.
Oil rose in price on Thursday due to disruption of supplies through the Baku-Tblisi-Ceyhan pipeline following an explosion on Monday in Turkey.
Analysts are also concerned that fighting in the South Ossetia region could disrupt energy exports from the Caspian region that travel through Georgia.