The number of bets for oil to hit US$150 a barrel, a level that many economists agree would hasten a global recession, have ballooned by nearly a third after the tightening of sanctions against Iran.
Options to buy crude next December at that price - about 50 per cent above today's levels - have risen in volume by 29 per cent since the release of a UN agency report on Iran's nuclear programme that prompted the US and other nations to boost sanctions on the country's energy and finance sectors.
The EU has applied more sanctions but has yet to place an oil embargo on Iran, which is Opec's second-biggest producer at 3.5 million barrels per day (bpd), about a quarter of which goes to Europe.
"It is really very difficult to replace these 865,000 barrels that come to Europe," Abdalla El Badri, the secretary general of Opec, said in Doha this week. "Europe now is facing some difficulties as far as sovereign debts and unemployment, so to cut these 865,000 barrels, I think it will be a problem,"
West Texas Intermediate, the US benchmark, was last trading at $100.49 a barrel. Brent crude was at $110.60 yesterday.
The November 8 report from the International Atomic Energy Agency, the UN nuclear watchdog, suggested that Iran was or had been developing an atomic weapon, although Tehran says its nuclear programme is peaceful.
This week the managing director of the state-owned Iranian Central Oil Fields Company announced plans to increase pumping by 45,000 bpd by early next year, while another official raised the spectre of oil at $250 a barrel if exports from Iran were completely blocked.
"As soon as such an issue is raised seriously, the oil price would soar to above $250 a barrel," Ramin Mehmanparast, a spokesman for Iran's foreign ministry, was quoted as saying by Fars News Agency. "I do not think the situation in the world and especially in the West today is adequately prepared to raise such discussions."
Among Opec nations, Libya is still working to bring its capacity back to levels from before this year's civil war. Saudi Arabia, which has most of Opec's spare production capacity, is pumping at its highest level in more than three decades, reducing its ability to inject further large volumes of oil into the market if Iranian supplies were to be cut off.
"It would be potentially disastrous," said John Tottie, an oil and gas analyst at HSBC in Riyadh.
"That's unlikely to happen," he said, "because as long as there's a willing buyer, the effectiveness of the sanctions are significantly reduced."
* with Bloomberg News