Opec's high price strategy could be strained to breaking point next year as a gathering rush of rival oil supplies overwhelms the cartel's ability to push up prices by restraining output.
The Organisation of Petroleum Exporting Countries defied calls to free more crude for winter - a decision ministers will have to justify to major oil consuming nations at the International Energy Forum in Osaka which started on Saturday.
While Opec's tough line is expected to hold benchmark US prices near $30 a barrel in the short term, modest world economic growth means it will soon find demand for its oil crowded out by growing Russian and West African flows, energy analysts said.
Already capping world oil demand, high prices now will only bring forward the day when cartel powerhouse Saudi Arabia is faced with the decision of whether to elect for a stretch of lower prices to weed out higher-cost non-Opec oil.
"The only response available to Saudi Arabia is to use a period of very low oil prices to curb non-Opec production and to slow capacity additions within Opec itself," said Roger Diwan of Washington's Petroleum Finance Company.
Sceptics have been predicting a sticky end for Opec's $22-$28 target ever since the cartel began to cut production to the bone three years ago to rescue their oil-dependent economies from a vicious market slump.
Opec's agreement on Thursday to leave output unchanged for the fourth quarter kept the heat under high oil prices. US crude on Friday traded at $29.50 a barrel, valuing Opec's index of mostly heavy oils near the top end of its target range.
That's too high for Opec's own good, oil experts said, because it both encourages more production in other producing countries and stifles fuel demand in industrialised nations.
"Next year's a tough call. There's definitely a big chunk of non-Opec production coming on," said Sarah Emerson of Energy Security Analysis in Boston.
"The question is can demand growth outstrip that?" Emerson said. "If the demand takes off which is unlikely, Opec is saved."
Up to a million barrels per day of new oil is due from rivals such as Russia, Angola and Kazakhstan next year, while Opec's production is stuck at the lowest level in a decade.
Despite high prices, the curbs are putting the group's own unity under pressure. Member countries like Nigeria and Algeria are clamouring to release new production capacity financed by foreign companies.
Saudi Arabia - which holds more spare capacity than the rest of the group combined - must soon choose whether to change tack.
"For the Saudis, there are tough choices ahead: mid-$20s oil prices are crimping demand and stimulating excess capacity growth. When do they play for a soft oil price landing to restore the balance?" asked Adam Sieminski of Deutsche Bank in London.
Opec has more than enough cheap oil on hand to drive out other producers. Saudi production costs are only about $1 a barrel compared to $10-$15 for most non-Opec nations.
But Riyadh needs at least $20 oil to finance the huge costs of running a welfare state where government salaries eat up a vast portion of national wealth.
Since Opec started cutting output in 1998 its market share has fallen to barely a third of the world's 76 million barrels a day of demand, despite Opec's grip on two thirds of global reserves.
The group late last year briefly abandoned its central $25-a-barrel target when the world economy slowed and as Opec threatened Russia with a price war unless it cooperated with production restraints for a few months.
Those cuts took Opec output to the lowest in a decade and combined with sustained Middle East tension won Opec a reprieve by securing a third straight year of high prices.
If the risk premium now in oil prices for fear of a war in Iraq deflate next year, the cartel could be saddled with the worst of both worlds - lower market share and a falling price.
And if Iraqi oil exports - running this year run at barely half of its two million bpd capacity - bounce back quickly after any military conflict then Opec may face little option but to abandon its price target.