Oil prices surged to a new record after an unexpected fall in US crude stockpiles added to fears over supplies for the winter months ahead.
Traders are watching developments on the Turkish border
US light sweet crude rose $3.36 to $90.46 a barrel by close of trade in New York, having traded as high as $90.60 earlier in the day.
Meanwhile London Brent closed $3.11 higher at $87.48,
Tensions along the Iraqi border between Turkey and Kurdish rebels have also played a part in the price rally.
US crude oil stocks fell by 5.3 million barrels last week, government data showed, when analysts had been expecting a rise in inventory.
Prices had retreated from last week's high, after concerns about the health of the US economy and expectations of more output from Opec.
A weaker US dollar makes oil a more attractive investment for holders of other currencies.
Despite the surge members of oil producing cartel Opec said they would stick to existing production targets.
The group has already said it would increase production by 500,000 barrels a day starting from 1 November, but the US is calling for an additional rise.
Eric Wittenauer of AG Edwards said: "I think this is a continuation of yesterday's rally off the surprisingly bullish inventory release."
Since the start of 2002, oil prices have increased more than four-fold, and in the period since January, the rise has been around 45%.