Oil fell on Tuesday amid concerns over the outlook for crude demand, but prices were supported after Washington announced new sanctions on Iran amid mounting tensions in the Middle East.

Benchmark Brent crude futures were down 57 cents, or 0.9%, at $64.29 a barrel by 0342 GMT. They dropped 0.5% on Monday, Reuters said.

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U.S. crude futures were down 58 cents, or 1%, at $57.32 a barrel. The U.S. benchmark rose 0.8% in the previous session.

Brent climbed 5% last week and U.S. crude surged 10% after Iran shot down a U.S. drone on Thursday in the Gulf, adding to tensions stoked by attacks on oil tankers in the area in May and June. Washington has blamed the tanker attacks on Iran, which denies having any role.

Weak manufacturing data released on Monday by the Federal Reserve Bank of Dallas added to worries about slipping demand for crude oil.

However, supply is expected to remain relatively tight, as the Organization of the Petroleum Exporting Countries and its allies including Russia, an alliance known as OPEC+, appear likely to extend a deal on curbing output when they meet in Vienna on July 1-2, analysts said.