Benchmark crude for March delivery was down 61 cents at $99.23 a barrel at late afternoon Singapore time in electronic trading on the New York Mercantile Exchange. The contract rose $1.13 to settle at $99.84 on Thursday.
Brent crude was down 37 cents at $118.22 a barrel on the ICE Futures Exchange in London.
Crude has bobbed around $100 for the last few months, buoyed by signs the U.S. economy is improving. On Thursday, the U.S. reported that the number of Americans seeking unemployment benefits fell to near a four-year low last week, suggesting the job market is gaining strength.
"The energy market appears positioned for additional price gains as we still look for crude to work its way up to the $101 area," energy consultant Ritterbusch and Associates said in a report.
Oil has risen from $96 earlier this month on growing investor optimism Greece may avoid a chaotic debt default. Greece agreed on Thursday to new spending cuts and other austerity measures that were necessary to receive an international bailout.
However, hours later, European ministers said Greece didn't go far enough and demanded more cuts within a week in exchange for a 130 billion euro ($170 billion) bailout to stave off bankruptcy.
In other energy trading, heating oil was down 0.7 cents at $3.20 per gallon and gasoline futures fell 1.4 cents to $3.00 per gallon. Natural gas slid 0.7 cents to $2.47 per 1,000 cubic feet.
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