Worries about the dollar overshadowed the opening of Opec's head of states summit on Saturday, after a warning by a senior Saudi minister that the US currency could "collapse" if the oil cartel mentioned its weakness in the leaders' closing declaration.

In a landmark summit, leaders of the Organisation of the Petroleum Exporting Countries are meeting in Riyadh, Saudi Arabia, were divided over how they should respond to the weakness of the US dollar, which has fallen 16 per cent this year against a basket of leading currencies.

The dollar has dropped 44 per cent against the euro since Opec leaders last met in Caracas, Venezuela in 2000. Opec members are also divided about whether the group should seek to play a greater role in world politics as well as in the oil market.

The disagreement was revealed when a ministerial meeting Friday afternoon, supposed to be in closed session, was accidentally broadcast live to reporters for about 30 minutes, before Saudi officials cut off the transmission.

The Iranian and Venezuelan ministers called for more radical measures and a specific mention of the effect of the dollar to be added to the draft declaration.

However, Saud Al-Faisal, the Saudi foreign affairs minister, warned the meeting: "The mere mention that Opec is studying the issue of the dollar is going to have an impact." He said a reference to the US currency in the declaration could cause the dollar to "collapse".

Analysts said that Mr Al-Faisal’s comments reflected they thinking of other policymakers, also worried about the rapid decline of the dollar, but concerned about the potential impact any reference to it would have on currency markets.

Price hawks such as Iran have argued that the dollar's fall justifies a higher oil price. An Iranian official pointed out on Friday that in euros the average price of oil for the year to date was significantly below the average for last year.

Iran wanted to raise attention to the effect of the weak dollar on oil-producing countries' revenues, but it will not push harder to include it on the final declaration, an Opec delegate told the Financial Times, suggesting that Iran would be satisfied with having made the point that the group should welcome a higher price of oil as a way to offset the weaker US currency.

Katherine Spector, of JP Morgan in New York, said that pricing oil in non-dollar currencies has long been threatened and even invoked by certain producer countries, mainly as a political statement.

"However, we continue to believe that a more widespread shift on pricing is both impractical and unlikely in the near term," Ms Spector said in a report.

The draft agreed by ministers on Friday night did not include any reference to the dollar. Saudi Arabia wants to avoid precipitating a further decline in the US currency that would cut the value of its dollar-denominated assets.

Its official reserves have been estimated at $277bn by the International Monetary Fund. The accidentally publicised dispute overshadowed the opening of the summit, only the third in the 47-year history of the organisation. The declaration is expected to highlight Opec's commitment to provide long-term security of supply, in an attempt to reaffirm the central role of oil in the world economy for decades to come. The cartel should try also to position itself on the climate change debate, seeking to protect the use of fossil fuels through technologies such as carbon storage.

Any decision on short-term production levels has been deferred to the ministerial meeting in Abu Dhabi on December 5, in spite of strong pressure from consuming countries, led by the US.

Opec has said that the market is well supplied and there are "no shortages of oil". It has blamed peculation, the weakness of the US dollar and geopolitical tensions for the 50 per cent price increase since the beginning of the year. West Texas Intermediate crude oil on Friday rose $1.93 to $95.36 a barrel.

Speaking on Friday before the ministers met, Chakib Khelil, Algeria's oil minister, highlighted the issue of security of demand for oil, saying that while Opec would promise to invest in new capacity, consuming countries should also assure the cartel that oil demand would not evaporate as a consequence of alternative energies and the fight against climate change.

He also suggested that Opec, which controls 40 per cent of the world'soil output, would use its declaration to reposition itself at the centre of the climate change debate, pushing for technologies to clean up fossil fuels through capture and storage of carbon dioxide emissions.