Oil prices slipped on Thursday, backing off from earlier gains spurred by tension around northern Iraq following the Kurdistan region's vote in favor of independence.
Crude has risen sharply in the last two-and-a-half weeks, in anticipation of renewed demand from U.S. refiners in the wake of Hurricane Harvey, and expectations for ongoing efforts by major world producers to limit supply.
However, both benchmarks are near overbought levels, based on an index of relative strength, which measures the speed and magnitude of price movements. U.S. crude has gained 9 percent in the last 14 trading days, while Brent is up 7 percent in that time period.
"We've made a really impressive run here and I do think we're due for a pullback," said Robert Yawger, director of energy futures at Mizuho in New York.
U.S. light crude ended Thursday's session down 58 cents, or 1.1 percent, at $51.56 after reaching a five-month intraday high of $52.86 a barrel.