OPEC believes oil prices could go as high as $170 a barrel this year
Crude oil prices have surged to near $144 a barrel as producing nations and the world's largest oil firms meet in Madrid to discuss soaring prices.
General concerns over global supplies and escalating rhetoric between Iran and Israel have pushed prices to fresh highs in recent days.
US light, sweet crude rose as much as $3.46 to a record $143.67 a barrel.
The price later fell below $140 after figures showed demand for oil in the US had fallen in April.
The US Energy Information Administration said demand was 19.76 million barrels per day in April, 3.9% lower than a year earlier.
The release of the monthly data caused oil prices to fall. In New York, US light, sweet crude fell by about $1 to $139.17.
In London, Brent crude, which had climbed as high as $143.81 a barrel, was trading at $139.54 after the figures were released.
A combination of the weak US dollar, surging demand and concerns about supply disruptions in the Middle East and Africa have forced prices up more than 40% this year.
In the latest war of words between Israel and Iran about the latter's nuclear intentions, a commander of Iran's revolutionary guard was quoted as saying that it could take control of the vital Strait of Hormuz waterway if attacked by Israel.
More than 60% of the world's oil is transported through the Strait, making its smooth functioning vital to the global oil markets.
Recent commitments by Saudi Arabia to increase production have seemingly done little to assuage concerns about the global availability of oil.
Measures to combat high prices and to increase long-term supplies were top of the agenda at the World Petroleum Congress in Madrid, which began on Monday.
Ministers from Opec nations again came under pressure to boost output, although many officials continue to blame market speculation from the rise in prices this year.
Many leading oil producers take a different view.
"This is not a speculative bubble," BP chief executive Tony Hayward told the meeting.
Alluding to differences of opinion among Opec members about how much oil to pump and what should be a reasonable price for oil, Mr Hayward said the industry's "problems are above ground not below it".
Experts added that the meeting must address where long-term growth in energy supply should come from and the environmental costs involved.
"Increasing population growth, energy intensity and globalization has led to a phenomenal rise in the use of energy," said Randy Gossen, president of the World Petroleum Council.
"The challenge for our industry is to ensure continuous, affordable and reliable energy supply in a sustainable, transparent and ethical, environmentally sound manner."