Opec, for sure, is caught in a Catch-22 bind. With just one day left for the producer group’s 166th meeting in Vienna, the most significant - and contentious - in its recent history, a defining decision has to be made. Cut production to raise prices, but loose the market share to non-Opec producers; or keep output level lower enough to make life harder for US shale players, but live with lower prices in the short-to-medium term.

Over the years, GCC countries have built fiscal reserves estimated at $2.45tn compared with the combined Gulf GDP of $1.64tn last year; they could weather a prolonged period of lower prices. In contrast, production and exports from Iran, Iraq, Libya, Venezuela and Nigeria have been hit by war, sanctions, unrest and mismanagement. None of them has significant foreign exchange reserves to withstand the impact of cheaper oil.

Longer term, Gulf states might feel the heat too. According to Standard & Poor’s, a prolonged decline in oil prices will likely slow the Gulf Co-operation Council economies and impact their massive infrastructure projects. S&P views Bahrain and Oman, with a breakeven oil prices of $138 and $118 respectively, as the most vulnerable; Qatar and the UAE the least.

Opec’s poorer members, led by Venezuela and Ecuador, have called publicly for an output cut, while Iran has hinted at the need. But the Gulf members, led by Saudi Arabia, are rejecting calls to pump less unless they are guaranteed market share in a highly competitive scenario. Separately, non-Opec Russia has hinted at cutting its oil production in a bid to revive falling prices.

The market, however, is awash with conflicting theories to deconstruct the perceived impact of the Opec decision. Some commodity fund managers believe oil could plunge to $60 per barrel if Opec does not agree a significant output cut; but $60 is highly far-fetched, say some others.

To have any impact, Opec would need to cut at least 1mn bpd; but there’s no guarantee prices would bounce back even with a higher reduction if unrestricted non-Opec supply is factored in. A “large” production cut by Opec to prop up crude prices may lead to an expansion of shale oil in the US where daily crude output has climbed to 9.06mn.

There is, however, one consensus: Opec can’t balance the market alone. The global glut of crude, which has contributed to a 30% decline in prices since June 19, has made Opec dependent on non-members to shore up the market, said Qatar’s former deputy prime minister and minister of energy and industry HE Abdullah bin Hamad al-Attiyah, who participated in the group’s policy meetings from 1992 to 2011.

The 12-member Organisation of the Petroleum Exporting Countries still produces around 40% of the world’s oil and hold 80% of its oil reserves, making its every move significant. But the alliance has to face the new reality. Opec is still relevant, but in different ways.

“If Opec asked me for an advice, I’d tell them, ‘Look, you can’t do it alone, you need to seek help from non-Opec producers and make everyone share the responsibility,’” al-Attiyah said in the Bloomberg interview.

Whichever way the decision goes, oil market will never be the same again.