Oil prices slipped on Thursday, as traders took profits after a recent rally.

U.S. crude oil climbed to three-week high in the previous session, as escalating turmoil in the Middle East provided support in the market.

The Iraqi forces completely ended major operations to recapture disputed areas claimed by Baghdad and the semi-autonomous region of Kurdistan, the Iraqi military said on Wednesday.

Meanwhile, local media reported Iranian Supreme Leader Ayatollah Ali Khamenei said Wednesday that Iran will cut 2015 international nuclear deal into shreds if the United States chooses to tear it up.

Analysts said an upward momentum in oil market appeared to be waning, as invests took profit after recent gains.

The West Texas Intermediate for November delivery was down 0.75 U.S. dollar to settle at 51.29 dollars a barrel on the New York Mercantile Exchange, while Brent crude for December delivery lost 0.92 dollar to close at 57.23 dollars a barrel on the London ICE Futures Exchange.