U.S. crude fell by nearly $1 a barrel on Friday as traders took profit at the end of the month, but remained in the middle of a month-long trading range underpinned by supply worries and strong gasoline demand in the United States, the world's top oil consumer.
Brent also fell in range bound trade, but was supported by energy supply concerns as fighting continued in eastern Ukraine. Kiev's defense minister promised to push ahead with an offensive against rebels until "normal life" was restored.
Russia has warned that it will cut natural gas supplies to Ukraine in June over Kiev's gas debt, raising the possibility of deliveries to Europe being affected. But a European Union official said Friday he hopes to reach a deal by June 3.