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U.S. oil slides to 6-1/2 year low under $42 as stocks build

Offshore oil platforms are seen at the Bouri Oil Field off the coast of Libya August 3, 2015. REUTERS/Darrin Zammit Lupi

By Barani Krishnan

NEW YORK (Reuters) - U.S. oil prices tumbled more than 3 percent to a 6-1/2-year low under $42 (27 pounds) a barrel on Thursday as data showing a big rise in key U.S. stockpiles intensified worries over a growing global glut.

A rise in the dollar (.DXY), after news of higher U.S. retail sales in July and strengthening employment data, added to the weight on oil. [USD/]

Oil has fallen by nearly a third since late June, a decline that continued this week after a spate of refinery outages sapped demand for crude. The largest of those refineries - BP PLC's (BP.L) 413,500-barrel per day (bpd) facility in Whiting, Indiana, also the biggest in the U.S. Midwest - has been forced to shut two-thirds of its capacity for repairs to a leak that could last a month or more.

Losses deepened on Thursday after market intelligence firm Genscape reported that stockpiles at the Cushing, Oklahoma delivery point for U.S. crude futures rose more than 1.3 million barrels in the week to Aug. 11, adding to concern that the Whiting outage was pushing up the surplus in crude. If confirmed, the Cushing build would be the biggest since March.

U.S. crude (CLc1) settled down $1.07 at $42.23 a barrel, after setting a session bottom at $41.91, its lowest since March 2009 when the financial crisis was wreaking havoc on oil prices.

The market could see a cascade of sell orders from now on, driving prices even lower, as more technical levels are broken, some analysts said.

"We are in the camp where prices will retest and fail to hold support at these levels," said Chris Jarvis of Caprock Risk Management in Frederick, Maryland. "We're likely get a capitulation trade in the $30 levels, a call we have been making since March."

Global crude benchmark Brent (LCOc1) settled down 44 cents, or almost 1 percent, at $49.22, ahead of Friday's expiry of its front-month contract. Brent's premium to U.S. crude (CL-LCO1=R) hit a three-week high of nearly $7.

Sentiment in oil has been so weak that prices failed to rally even after Wednesday's data from the U.S. Energy Information Administration (EIA) showing a 1.7 million-barrel drop in crude stockpiles last week.

The EIA added to concern about the growing supply glut in oil on Thursday, reminding the market that Iran could boost output by 100,000 bpd this year with an easing of nuclear-related sanctions on Tehran's exports.

(Additional reporting by Libby George and Lisa Barrington in London, and Henning Gloystein and Jacob Gronholt-Pedersen in Singapore; Editing by Marguerita Choy and Frances Kerry)