Ali al-Naimi, the Saudi oil minister, told reporters that "fluctuations in the market have nothing to do with Opec," saying there were many other factors affecting prices.

Sticking to the dollar

The summit saw Saudi influence within the group prevail over the demands of an anti-US bloc to make the oil exporters' group more political.

Hugo Chavez, the Venezuelan president, had opened the summit on Saturday urging the grouping to be a "geopolitical agent," which earned a gentle rebuke from his Saudi host, King Abdullah.

The newly enlarged group which accounts for 40 per cent of world oil supplies did not adopt an Iranian proposal to abandon the US dollar to price oil.

The statement, which also included support for "clean oil", called for more action to fight poverty and expressed concern over global climate change.

The call to combat global warming came as Kuwait, the United Arab Emirates and Qatar each pledged $150m towards research into climate change and the environment, and Saudi Arabia said it would give $300m.

'Special tax'

Other leaders were reluctant to make similar promises.

"We are not committing anything. We don't know what the proposal is," Chakib Khelil, the Algerian energy minister, said.

Rafael Correa, the president of Ecuador, told reporters on Sunday the world's richest nations should pay for the protection of the environment in the world's poorest countries.

He proposed a special tax on oil-consuming nations to pay for environmental protection elsewhere, with Opec overseeing spending.

"It annoys us a bit, all this moralising 'don't cut down your trees' from the first world, when they've already done it," Correa said. "If Europe wants to breathe pure air from Amazon countries, then the Amazon countries shouldn't have to pay for it."

Opec did not adopt a resolution proposed
by Iran to drop the dollar [AFP]
Elsewhere on the sidelines of the summit Ahmadinejad said that Iran never wanted to use oil as a weapon, but if the US attacked the country, it would "know how to react".

"We would never want to use oil as a weapon or take any illegal actions ... but if America takes any action against us, we will know how to reply," he said.

Fears that a US attack on Iran could lead the country to stop its exports or block shipping channels for oil tankers is one of the factors that has driven oil prices to record highs in recent years.

He predicted, however, that conflict would not break out.

"My prediction is that no war will break out in the region," he said.

Ahmadinejad also talked of his plan for oil exporters to abandon the US dollar as the currency they use to price and sell their crude.

"The meeting decided to direct our ministers of finance and foreign affairs to talk about this and later produce their findings," he said.

Libya said the next Opec summit will be held in the country in 2012.