Crude oil futures fell as much as 3 percent o n T hursday, heading for the worst quarterly performance since the 2008 financial debacle, on worries that an EU summit will not find durable solutions to the euro zone crisis, stifling global growth prospects.
Weaker U.S. equities on Wall Street after the U.S. Supreme Court decision upholding key elements of President Barack Obama's healthcare reform law added to the day's pressures on crude futures.
Despite recent gains, Brent crude futures were on track to end the second quarter with a drop of about 25 percent, the worst since the last quarter of 2008, at the height of the financial crisis after the collapse of Lehman Bros.
U.S. crude futures, meanwhile, were poised to see a fall of about 24 percent, also the biggest quarterly loss since the last quarter of 2008.
Trading on Wall Street was volatile, with healthcare stocks hit after the Supreme Court upheld the centerpiece "individual mandate" provision of the Obama healthcare overhaul. Equities were already lower on skepticism that the European Union Summit will result in concrete measures.
"It's the euro zone problems, the strength of the dollar and the weak equities, said Stephen Schork, president of the Schork Group in Villanova, Pennsylvania, commenting on the reasons for the day's price drop.
The euro fell against the dollar on doubts about the outcome of the EU summit, denting investors' interest in buying riskier assets such as oil and other commodities.
In London, Brent crude oil futures for August settled at $91.36 a barrel, dropping $2.14, after having slid to a session low of $90.88.
U.S. August crude fell to an eight-month low, closing at $77.69 a barrel, down $2.52.
"The further fall in equities triggered by the Supreme Court decision ... exerted selling pressure on crude futures," said Addison Armstrong, director of market research at Tradition Energy in Stamford, Connecticut.
Technical support for U.S. crude at around $79 was breached in the surge of selling after equities slid further, Armstrong said.
Trading volumes were light, with Brent crude nudging up 1 percent against its 30-day average while U.S. crude volume was down 2.5 percent against its 30-day average, according to Reuters data.
Brent's premium against U.S. crude widened to $13.67 against $13.29 on Wednesday, as U.S. crude having fallen faster than its London counterpart.
Economic data released on the day also weighed on crude futures. U.S. GDP for the first quarter grew at a 1.9 percent annual pace, but consumer spending and export growth were not as robust as previously thought.