rude for September delivery was last down 53 cents to $66.22 a barrel in electronic trading on Globex.
"Given market participants' wariness regarding the prospects for economic recovery at the moment, crude prices are vulnerable to a further sell off towards the $63.87 correction level, especially if we see poor U.S. housing data and further stock builds later today," wrote Nimit Khamar, analyst at Sucden Financial Research, in a note to clients.
Trading was volatile early Tuesday, with oil futures moving in and out of positive territory several times.
The Commerce Department estimated Tuesday that U.S. housing starts fell 1% in July to a seasonally adjusted annual rate of 581,000 from an upwardly revised 587,000 rate in June.
Separately, data showed that producer prices fell 0.9% in July, after seasonal adjustments, as prices for energy and food dropped.
Supply data ahead
The American Petroleum Institute will release data on petroleum inventories Tuesday afternoon, while the Energy Information Administration will report its more closely watched data on Wednesday morning.
Analysts polled by Platts expect the data to show that crude stocks rose by 1.1 million barrels during the week ended Aug. 14. They also project a decline of 1.7 million barrels in gasoline stocks as well as a build of 800,000 barrels in distillate stocks.
Refinery utilization rates are expected to increase by 0.25 percentage point to 83.75%.
Also on Globex, September reformulated gasoline fell 1.8% to $1.9162 a gallon and September heating oil dropped 1.7% to $1.7950 a gallon.
September natural-gas futures fell 0.1% to $3.152 per million British thermal units.
