Oil fell this morning 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 34 cents, or 0.5%, at $64.52 a barrel in early trade. They had dropped by 0.5% yesterday.
US crude futures were down 24 cents, or 0.4%, at $57.66 a barrel. The US benchmark rose 0.8% in the previous session.
Brent climbed 5% last week and US crude surged 10% after Iran shot down a US 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.
US President Donald Trump targeted Iranian Supreme Leader Ayatollah Ali Khamenei and other top Iranian officials with sanctions yesterday, taking an unprecedented step to increase pressure on Iran after Tehran's downing of the drone.
Trump also said on Twitter that other countries should protect their own oil shipping in the Middle East rather than have the United States protect them.
Meanwhile, hopes are waning for progress in Sino-US trade talks at this week's G20 meeting as investors await a meeting between Trump and Chinese President Xi Jinping.
That could further hurt global growth prospects, hitting demand for oil and other commodities.
Weak manufacturing data released yesterday 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 on July 1-2 in Vienna, analysts said.
Russian Energy Minister Alexander Novak said yesterday that international cooperation on crude production had helped stabilise oil markets and was more important than ever. He also voiced concerns about demand.
Sanctions on Iran and Venezuela imposed by Washington have cut oil exports from the two OPEC members but US production has been rising, leading some Russian officials to accuse Washington of carving out market share for its energy exports.