US oil fell 6 cents, or 0.1 percent, to $56.65 a barrel by 0050 GMT.
Brent crude was down 10 cents, or 0.2 percent, at $60.98, after adding 1 percent on Thursday.
The approach of Hurricane Dorian toward Florida raised fears that offshore US crude producers may slow output if the storm passes into the Gulf of Mexico over the weekend.
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