Prices for crude climbed briefly above $45 US a barrel on Thursday on new concerns over the future of Russian producer Yukos and attacks on Iraq's oil infrastructure.
The prices of light crude for October delivery hit an intraday high of $45.37 US before pulling back to $44.06 US, up 6 cents from Wednesday.
Yukos, the biggest oil producer in Russia, warned it may not be able to pay wages. The oil company owes $3.4 billion US to the Russian government. A court has ordered some of the company's assets frozen, a move Yukos has said could affect its production.
Also driving oil prices on Thursday was a new report of sabotage against pipelines in Iraq. A pipeline near the northern city of Kirkuk was reported to have been attacked.
The crude oil future contract jumped $1.88 US on Wednesday after the U.S. Energy Department said crude inventories dropped by 4.2 million to 287.1 million barrels last week. Analysts had been expecting inventories to remain steady or rise.