On the New York Mercantile Exchange, light sweet crude futures for delivery in October traded at USD107.71 a barrel during U.S. trading, down 0.82%.
The October contract settled up 0.97% at USD108.60 a barrel on Thursday.
The commodity hit a session low of USD107.24 and a high of USD108.81.
U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov held a fresh round of talks on Friday to discuss ways to disarm Syria of its chemical weapons, and while the U.S. says military action is still possible, energy markets concluded such campaigns are less likely.
Syria has agreed to hand over its chemical weapons cache to international control at Russia's request.
Oil prices have shot up during the crisis amid fears a U.S. strike on Syria will engulf the oil-rich Middle East and threaten global supply.
Elsewhere, the Thomson Reuters/University of Michigan preliminary U.S. consumer sentiment index fell to a six-month low of 76.8 in September from 82.1 in August, worse than expectations for a decline to 82.0.
The news sent oil prices falling by stoking fears that the U.S. still faces potholes along its road to recovery and will demand less fuel and energy going than once thought.
Elsewhere, official data showed that U.S. retail sales rose 0.2% in August, missing expectations for a 0.4% rise after an upwardly revised 0.4% increase the previous month.
Core retail sales, excluding automobiles, rose 0.1% last month, short of expectations for a 0.3% gain after an upwardly revised 0.6% increase in July.
A separate report showed that the U.S. producer price index rose 0.3% in August, more than the expected 0.2% after a flat reading the previous month.
Core producer price inflation, excluding food and energy, was flat last month, compared to expectations for a 0.1% rise, after a 0.1% gain in July.
Meanwhile on the ICE Futures Exchange, Brent oil futures for October delivery were down 0.52% at USD110.95 a barrel, up USD3.24 from its U.S. counterpart.