Trading desks of oil major BP and merchants Vitol, Gunvor and Trafigura have recorded losses in the tens of millions of dollars each
The United States this week demanded countries halt imports of Iranian oil from November, a hardline position the Trump administration hopes will cut off funding to Tehran
Several members of the OPEC responded to Trump's tweet, saying prices were not artificially inflated
Last November, Opec along with Russia and a group of other producers extended an output-cutting deal to cover all of 2018
US output is still up by almost 16% since mid-2016
The deal to cut output expires in March 2018, but Opec will meet on November 30 to discuss its policy, with most analysts expecting some form of agreement to extend the cuts
US West Texas Intermediate crude futures hit $58.92 a barrel, their highest since July 2015
WTI has been buoyed by the shutdown of the 590,000 bpd Keystone pipeline, one of the largest crude pipelines from Canada to the United States