Oil declined about 5 percent on Tuesday after the International Monetary Fund cut its 2015 global economic forecast on lower fuel demand and key producer Iran hinted prices could drop to $25 a barrel without supportive OPEC action.
U.S. crude, also known as West Texas Intermediate or WTI, settled 4.7 percent lower at $46.39 a barrel, near its intraday bottom of $46.23.
was last down about 70 cents at $48 a barrel, after touching a session low at $47.78.
Genscape, an analytics firm that monitors U.S. oil stocks, reported a 2.6 million-barrel build last week in Cushing, Oklahoma, the delivery point for the U.S. crude futures contract, adding to the market's bearish sentiment, traders said.
Trade group American Petroleum Institute will issue its data on U.S. crude inventories for last week on Wednesday while the government's Energy Information Administration will release its stockpile tally on Thursday, both delayed a day by a holiday on Monday.
The premium for Brent crude over U.S. crude futures widened after Genscape's reported build in Cushing stocks. The arbitrage was up 20 percent to around $1.30 a barrel by 1652 GMT, after widening to as much as to $1.58 earlier.
Oil prices are hovering near six-year lows after a seven-month long selloff on worries of a glut caused primarily by unexpectedly high production of U.S. shale crude.
An expected slide in the U.S. oil rig count in the first quarter compared with the fourth quarter of last year also failed to boost sentiment on Tuesday as traders and investors remain glued on concerns of oil oversupply.
"Because we have record oil production now, the falling rig numbers are not creating an immediate positive impact in bolstering prices," said Phil Flynn, analyst at Price Futures Group in Chicago. "In fact, they may be creating just the opposite impact; reminding us how poor demand is."
U.S. oil services firm Baker Hughes Inc said in its conference call presentation on Tuesday the U.S. average rig count was expected to decline 15 percent in the first quarter from a quarter ago, and it expected to lay off some 7,000 staff.
Earlier data from Baker Hughes showed the number of rigs drilling for oil in the United States fell by 55 last week, the second-sharpest weekly drop in 24 years.
The IMF, in its latest World Economic Outlook report, reduced its forecast by 0.3 percentage points for this year and next, projecting a 3.5 percent growth in 2015 and 3.7 percent for 2016.
Iran's Oil Minister Bijan Zanganeh said Tehran saw no signs of a shift within OPEC toward action to support oil prices, and that the industry could ride out a further slump toward $25.