Brent crude closed 37 cents, or 0.5%, lower at $78.28 a barrel, while West Texas Intermediate crude fell 23 cents, or 0.3%, to $72.97.
On the supply side, worries of tightness after an unexpected draw in U.S. oil stockpiles and a halt to some Iraqi Kurdistan oil exports were partially offset by a smaller-than-expected output cut in Russia.
U.S. crude oil stockpiles fell unexpectedly last week, the Energy Information Administration said, as refineries ramped up operations after maintenance season and U.S. imports fell to a two-year low.
Supply concern were, however, eased by reports that Russian oil production fell by around 300,000 bpd in the first three weeks of March, less than the targeted cuts of 500,000 bpd.
A stronger greenback hurts oil demand as crude becomes more expensive for buyers who hold foreign currencies.