Crude for September delivery was as high as $47, nine cents on the New York Mercantile Exchange, a new record.
Adjusted for inflation, that is still about 18-percent cheaper than just before the first Gulf War.
In Iraq, fighting continued in the holy city of Najaf despite a peace proposal delivered by the Iraqi interim government to aides of a militant cleric. His followers have threatened to blow up oil pipelines, prompting a temporary stop to the flow of crude.
Traders are also anxious about the oil supply in Russia. The fortunes of oil giant Yukos took a turn for the worse when a court rejected the company's attempt to suspend government efforts to collect $3 billion in back taxes.
Yukos pumps about 1.7 million barrels a day.