USA crude production has hit record levels since late past year.
US West Texas Intermediate crude had lost 16c or 0.2% to $66.88 a barrel by 4.23am GMT, after falling nearly 2% on Thursday.
Over the last four weeks, motor gasoline product supplied averaged about 9.7 million barrels per day, up by 0.8 percent from the same period previous year.
The reserves fell by 3.6 million barrels, or 0.8 percent, to 434.5 million barrels (with a forecast of a decline of just 0.4 million barrels).
"You had the API showing a strong build in crude oil and nothing fantastic on the products", says Olivier Jakob, managing director of consultant Petromatrix GmbH.
Since the agreement took effect, global oil markets have tightened, which can be seen in the decline in crude oil and other liquids inventories following sustained increases in quarterly global liquid inventories from mid-2014 through most of 2016.
The discount between U.S. and Brent crude has now blown out to around $US11 a barrel, the largest it has been since mid 2015 and a sign the growing production and bottlenecks in pipelines and storage is now capping price growth and indeed putting downward pressure on U.S. prices.
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About 883,000 barrels per day (bpd) of USA crude is expected to land at Asian ports in June, up from 769,000 bpd in May, which was the previous high for US crude exports to Asia.
The trading sentiment dampened in futures trade after oil lost more ground on pressure from record U.S. production and expectations of higher OPEC output, analysts said. For the week, WTI was on track for a 2.5% fall, adding to last week's near 5% decline and shrugging off a 3.6 million-barrel drop in USA crude stockpiles last week. That was a rise of 215,000 barrels a day (bpd) over the 12 months. Surging output and a lack of pipeline capacity in the prolific Permian Basin shale play in Texas is exacerbating swelling USA inventories.
Now OPEC is facing the problem, if we really want to choke off American production, how low does the price have to go?'
The Houston-based oilfield services company Baker Hughes reported on Friday that there were now 861 rigs drilling for oil in the United States with more than half of them - 477 - situated in the western Texas Permian Basin. It was the eighth increase in nine weeks.
Saudi Arabia, effective leader of the Organisation of the Petroleum Exporting Countries (OPEC), and Russian Federation have discussed boosting output to compensate for supply losses from Venezuela and to address concerns about the impact of US sanctions on Iranian output.
The speculator group cut its combined futures and options position in NY and London by 50,937 contracts to 370,980 during the week.