Brent crude oil futures were at $73.71 per barrel, down 15 cents, or 0.2%, from their last close and nearly $1.8 below the November-2014 high of $75.47 a barrel reached the previous day, CNBC reported.
The latest figures from OPEC, for March, indicated that Iran produced around 3.8 million barrels of oil per day, making it the third largest oil producer in the 14-member group, after Saudi Arabia and Iraq. French President Emmanuel Macron's prediction that the USA will pull out of the Iran nuclear accord stoked concerns about a renewal of sanctions that would slash crude exports from OPEC's third-largest producer.
Soaring U.S. output has made WTI crude around $6 per barrel cheaper than Brent and drawn exports to record highs over 2 million bpd.
Trump will decide by May 12 whether to restore USA sanctions on Tehran, which would likely result in a reduction of its oil exports.
United States crude oil inventories rose by 2.2-million barrels in the week to April 20 to 429.74-million barrels.
The supply side-driven increase in crude oil prices is likely to spur a major differentiation in emerging markets' performance, hurting large net oil importers with weak economic fundamentals, possibly by more than it benefits large net oil exporters, the brokerage said.More news: Racist Promposal 'Under Investigation' at Florida School
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"We think at least 250,000 to 350,000 barrels of Iranian crude (a day) could be at risk of disruption if sanctions are brought back into place", Ehsan Khoman, head of research and a strategist at financial group MUFG, told CNBC's Capital Connection on Thursday.
Distillate stockpiles, which include diesel and heating oil, fell by 2.6 million barrels, versus expectations for a 861,000-barrel drop, the EIA data showed. That's an increase of more than a quarter since mid-2016.
Dutch bank ING said "the wide discount for WTI to Brent saw exports rising 582,000 bpd week-on-week to a record high of 2.33-million bpd".
"With US output surging, some analysts warn that the 20-percent climb in Brent prices since February is starting to look overdone".
Still others noted that the USA dollar hitting its highest level since mid January did little to damage crude's performance this week: "Oil has had a very good week so far given what the dollar has done", said Bill Baruch, president of Blue Line Futures, adding that "I expect the market to have a good finish for the week given the uncertainty around the Iran deal".