Brent crude futures settled at $73.21 per barrel, down 24 cents from their last close.
The U.S. has been unable to persuade China to cut Iranian oil imports, according to two officials familiar with the negotiations, reports Bloomberg.
Saudi Arabia has told OPEC in early July that it pumped 10.488 million barrels per day (bpd) of crude oil in June, an increase of 458,000 bpd from the level it said it produced in May, OPEC sources told Reuters on Thursday.
Still, with Russian Federation, the United States and Saudi Arabia now all producing 10 million to 11 million bpd of crude, just three countries now meet around a third of global oil demand.More news: At Ohio rally, Trump casts midterm elections as a personal referendum
U.S. West Texas Intermediate (WTI) crude futures CLc1 were up 37 cents, or 0.5 percent, at $68.86 barrel.
They said they remained committed to the 2015 accord and to building up economic relations with Iran, including "the continuation of Iran's export of oil and gas" and other energy products. Inventories rose for the first time in seven months in May.
A complete halt to Iranian supplies looks unlikely, with Bloomberg reporting China, Iran's biggest customer, has rejected a US request to cut imports from the OPEC member.
Saudi Arabia halted temporarily oil shipments through the lane on July 25 after attacks on two oil tankers by Yemen's Iran-aligned Houthi movement.
Fears that Chinese demand could taper fuelled the pullback on Friday after state oil major Sinopec cut its purchases of U.S. crude. Yet it was not immediately clear how long the suspension of USA oil imports would last.More news: Eleven children in US rescued from 'extremists' at 'filthy' hideout
China's largest refiner, Sinopec, will hold off on buying U.S. crude as the escalating trade battle threatens to make American imports more expensive, according to a person familiar with the matter.
Whilst exports of crude from the U.S. to China have grown exponentially in recent years, Leszczynski says the volumes are still pretty small from China's point of view.
Tamar Essner, an analyst at Nasdaq Inc., said there are "no signs whatsoever that this trade war is going to clear up anytime soon", and that has "caused investors to continue to trim net length, take profits, and de-risk that position with the sense that oil's upside is limited unless there's material reduction in Iranian barrels".
The official confirmed that during July delegations would be dispatched to Beijing and Delhi to press home the case, having already visited the capitals of other major Iranian oil importers.More news: Rio Ferdinand sends transfer message to Maurizio Sarri after Man City defeat