Rising tensions with Iran, after the world's No. 4 oil producer refused to accept inspections of its nuclear program that the West fears could be linked to weapons, stirred supply concerns from the OPEC nation.
Nigerian disruptions from militant attacks and a strike have also underpinned prices since late April, adding to gains that have sent prices for oil up about six-fold since 2002 as part of a wider commodity surge.
Growing demand from emerging markets like China has supported the oil rally, as supplies struggle to keep pace, with further strength for dollar-denominated commodities coming from the slumping greenback.
High oil prices have hit U.S. refiners' profit margins, prompting some to trim runs, but stoking supply concerns as the world's biggest oil consumer heads into the summer driving season. Speculators have also poured cash into commodities as a hedge against inflation since September.
The mounting supply problems and strong demand from emerging economies prompted Goldman Sachs to forecast oil could reach $200 a barrel within the next two years.
U.S. President George W. Bush is expected to talk with officials from OPEC kingpin Saudi Arabia about the effects of high fuel prices on the U.S. economy on his trip to the world's top exporter later this month.
Bush has called on the Organization of the Petroleum Exporting Countries to raise output to help bring down prices, but the cartel has blamed high prices on speculators and insists markets are well-supplied.
A weekly U.S. government report on fuel inventories due out Wednesday is expected to show a 1.6 million barrel build in crude supplies, an 800,000 barrel rise in distillate inventories and a 100,000 barrel decline in gasoline stocks, according to a Reuters poll.
