Brent crude slipped toward $109 a barrel on Thursday on rising U.S. oil stockpiles, while fears that the world's largest economy might miss a deadline for next year's budget and risk a recession also kept bulls in check.
Brent crude fell 19 cents to $109.31 a barrel by 1112 GMT, while U.S. crude was at $86.34, down 43 cents. The January Brent contract expires on Friday.
The U.S. dollar strengthening almost 0.2 percent against a basket of currencies also weighed on oil prices.
Deadlocked talks to avert a "fiscal cliff" of steep tax hikes and budget cuts in the United States returned to investors' focus after announcements by the U.S. Federal Reserve of more monetary stimulus buoyed global markets on Wednesday.
Failure to reach a compromise on the U.S. budget by the end of the year risks pushing the world's biggest oil consumer into recession and has stoked fears that a fragile recovery trend emerging in China and some other countries would be stifled.
Sharp differences on the 2013 budget persisted between Congressional Republicans and the White House on Wednesday, when negotiators warned the showdown could drag on past Christmas.
"People are worried about the economy, the fiscal cliff in the U.S. and the European economy still remains a tricky one," said Richard Langkemper, analyst at Argos North Sea Group in Rotterdam.
"Refinery margins in Europe are very thin at the moment," he added.
U.S. crude inventories rose last week against expectations of a fall while gasoline and distillates stockpiles jumped more than expected. The jump in fuel stocks came despite a pull-back in refinery output and steady import levels.
"You saw distillates stocks and especially gasoline going up, people may be worried about demand now," Langkemper said.
Demand will be sluggish through 2013 as economic expansion stays tepid and crude supply levels comfortable, which could ease price pressure on consumers, the International Energy Agency (IEA) said.
Global oil demand would grow 865,000 barrels per day in 2013 to hit 90.5 million bpd, the IEA said.
OPEC TARGET UNCHANGED
In Vienna, OPEC ministers agreed to retain the producer group's 30-million barrels-a-day output target and meet next on May 31.
"It became clear once again that the cartel is relatively unwilling to act, especially when prices are high," Commerzbank commodity analysts said in a note.
The target is higher than what is required from OPEC to meet demand next year, some market observers say, but the excess supply has cushioned the impact on prices from a sharp drop in Iranian oil exports due to sanctions this year.
Big powers hope soon to agree with Iran to hold a new round of nuclear talks in another bid to resolve a protracted dispute over Tehran's atomic programme.
Inspectors from the U.N. nuclear watchdog arrived in Tehran in the first such meeting since August to ease international concerns over Iran's disputed nuclear programme.
For oil products, U.S. heating oil and gasoline futures slipped after Wednesday's sharp gains following a fire at Motiva's refinery in Port Arthur, Texas, the largest in the United States.
Worries about supply disruptions kept losses in check as Syria's forces of President Bashar al-Assad have fired ballistic missiles against rebels in recent days, in what U.S. officials described as an escalation in the 20-month civil war. (Additional reporting by Florence Tan in Singapore; Editing by Alison Birrane and Jason Neely)