Oil prices breached a record high of $75 on Friday, raising concerns about its impact on world economic growth.

The powerful 11-member Opec cartel is expected to hold informal talks on Monday on the forum's sidelines but no decisions are expected on output that would give some comfort to frenzied oil markets.

Abdullah bin Hamad al-Attiya, Qatar's oil minister, said in his opening remarks: "No decisions or agreements will be made at the forum that will have any direct or quick influence on international markets or price levels."

This was confirmed by his Iranian counterpart.

"Opec is producing as much as it can and there is not a physical lack of oil, so I don't think there will be a change," Kazem Vaziri-Hamaneh said.

He said Iran, which is the world's fourth and Opec's second biggest crude producer, was close to its quota of around four million barrels a day.

"So Opec is doing its best at the moment, stocks are improving, the production level is appropriate."

He also said Iran's nuclear programme would be used to satisfy energy demand within the country, freeing up oil and gas supplies for export.

Tension

On Saturday, Vaziri-Hamaneh said without naming the United States directly, that countries who are trying to intimidate Iran over what it regards as its right to enrich uranium were the ones to blame for the nervousness that has rattled oil markets.

"Research in enrichment should not be the cause for that sort of tension, those who are escalating are the ones causing the tension," he said.

"We are moving within the framework NPT (Non-Proliferation Treaty) regulations and laws, we have to ask the question what is really the cause of the tension and who are the people who are intimidating us."

The West led by Washington has accused Iran of pursuing a nuclear weapons programme while Tehran insists its intentions are peaceful and civilian.

The UN Security Council has given Iran until Friday to halt enrichment activity.

Qatar's al-Attiya said that there was at least a $15 per barrel premium on oil prices related to political tension.

A senior US energy department official attending the Doha forum admitted that tension over Iran was affecting oil markets but that it was Iran's fault in initiating uranium enrichment in defiance of "the world".

Karen Harbert, assistant secretary for policy and international affairs, said: "I think the world has spoken out about its feelings [over Iran] and unfortunately there is a reaction in the market."

The forum, going on until Tuesday, brings together some of the world's largest producers and the chief executive officers of several oil giants.