Mahmoud Ahmadinejad, the Iranian president, has called on Opec members to stop pricing oil in "worthless" US dollars.

"They get our oil and give us a worthless piece of paper," he told reporters at the close of a two day meeting of the Organization of Petroleum Exporting Countries in Saudi Arabia.

The fall in the value of the dollar has weakened the purchasing power of Opec members and helped push oil prices to nearly $100 a barrel.

Ahmadinejad is to meet Hugo Chavez, the Venezuelan president, later on Monday to discuss the issue.

Chavez echoed Ahmadinejad's sentiment, saying "the empire of the dollar has to end".

Opec's summit in Riyadh ended on Sunday with leaders divided over whether to dump the dollar as a currency to price and sell oil.

Both Iran and Venezuela have proposed trading oil in a basket of currencies to replace the falling dollar, but a final statement from Opec after the meeting did not include any reference to the weakening dollar.

Instead Opec vowed to keep providing Western consumers with an "adequate" supply of oil.

Saudi Arabia, a staunch ally of the US, had opposed the move to include concerns over the falling dollar included in the summit's closing statement and tried to direct the focus of the summit towards studying the effect of the oil industry on the environment.

Falling dollar

But both Iran and Venezuela made it clear that they would press for action on the dollar, which could include pricing oil in a basket of currencies.

"There was a proposal from Iran and Venezuela to have a basket of currencies for the pricing of OPEC oil," Bayan Jabor, the Iraqi finance minister, said.

"But a consensus could not be reached," he said, adding that backed by Ecuador, the two had won agreement that finance ministers would discuss the issue before a scheduled oil ministers meeting in Abu Dhabi on December 5.

"Because the final communique was already drafted, there was an agreement that Opec finance ministers hold a meeting before the oil meeting in the UAE in December to discuss economic issues including the dollar's exchange rate."

The Venezuelan leader had opened the summit urging Opec, which accounts for 40 per cent of world oil supplies, to be a "geopolitical agent".

Chavez lauded Opec's ability to ensure high oil prices for developing producer nations, saying Opec "must stand up and act as a vanguard against poverty in the world".

He threatened that if Washington follows through on military threats against Iran, oil could double to $200 a barrel.

The summit, only the third in the group's history, also acknowledged the oil industry's role in global warming, with pledges of cash for research into climate change.

PHOTO CAPTION

Mahmoud Ahmadinejad (L) and Hugo Chavez