West Texas Intermediate futures for August delivery rebounded to $52.52 (+1.68%); Brent crude advanced to $57.82 (+1.35%) after an Iranian diplomat hinted that investors might had been too sure of a deal. He said that Tehran would not be flexible regarding its "red lines".

Both crudes managed to advance despite Wednesday's data from the Energy Information Administration, which showed that crude inventories unexpectedly rose last week in the U.S.

Crude inventories rose by 384,000 barrels, compared with analysts' expectations for a decrease of 700,000 barrels. Crude stocks at the Cushing, Oklahoma, rose by 299,000 barrels. Gasoline stocks rose by 1.2 million barrels, compared with expectations for a 254,000 barrels drop. Distillate stockpiles, which include diesel and heating oil, rose by 1.6 million barrels, vs expectations for a 860,000 barrels gain. U.S. crude imports fell by 197,000 barrels per day.