Khalid al-Falih, Saudi Arabias energy minister, said the cartel, which controls about a third of the worlds oil production, was moving close to a deal, as he signalled that he was working to bridge a gap with regional rival Iran.
But he sought to manage expectations, saying he was not concerned about a no-agreement scenario, arguing the oil market was already moving back towards balance.
Bijan Zanganeh, Irans oil minister, said all Opec members were ready to compromise and there was a framework for a deal. His tone was notably softer than in recent days. He said the cartel was targeting 1m-1.2m barrels a day of cuts between its 14 members.
The ministers were speaking in Vienna where they are meeting to try to reach a deal to curb production and bring an end to a savage two-year downturn in prices that has shredded the budgets of its members. Any deal would mark a U-turn from a decision made in November 2014 to keep output high to put pressure on rivals.
Brent crude, the international oil marker, rose 8.5 per cent to $50.30 in early afternoon trading in London.The pressure is probably too great for them not to reach a deal, said Jason Schenker of Prestige Economics at the meeting in Vienna. At the end of this meeting the oil price could have a five handle or a three handle thats how big a potential swing were talking about.
In September Opec reached a provisional accord in Algiers to bring its total production down to between 32.5m b/d and 33m b/d from a near record 33.8m b/d at the moment. But two months later, the group has yet to agree on how the cuts will be apportioned.
A deal could help the oil market recover from its longest downturn in a generation, which has hammered the share prices of oil companies and sent big producing countries spiralling downwards into recession.
Saudi Arabia is expected to shoulder the burden of any production cuts along with its Gulf allies, and Mr Falih on Wednesday said its oil output would take a big hit.
In return, the kingdom has asked Iran to curb output at close to 3.7m b/d, although privately it has indicated it may allow a higher level near 3.8m b/d, which is close to its current rate of production, according to third-party assessments used by Opec.
Iran, which is finding its feet after years of western sanctions, initially said it should be exempt like conflict-ridden Nigeria and Libya. Later, however, it softened its stance, saying it would freeze its production closer to 4m b/d. Mr Zanganeh on Wednesday said Iran believed Opec should use so-called secondary sources as the basis of any agreement, a previous point of conflict.
Mr Falih told reporters that, based on Opec estimates, Iranian supply had recovered to pre-sanction levels and a freeze at this level would be well received by other members. Hopefully this will be the framework, he said.
Should Opec strike a deal on Wednesday, the Saudi energy minister said he expected Russia and other countries outside of the cartel to cut about 600,000 b/d of production. The kingdom believes the co-operation of big producers outside of the cartel is necessary for any deal to be effective.
But he also criticised Russias public stance that freezing its production, which has climbed to a post Soviet-era high, was acceptable.
Freezing at an all-time high is not a contribution. [Its] not a match to what Opec is doing. Our discussion with Russia has been about a cut from non-Opec, he said.
Yasser Elguindi at Medley Global Advisors said: The comments suggest there is a growing convergence on positions between Saudi Arabia and Iran, which is essential for any deal? The big surprise would be a Russian contribution not just to freeze but to join Opec in cuts.
Algerias energy minister Noureddine Boutarfa, one of the architects of the September accord to reduce output, said he was 99 per cent certain Opec would reach a deal on Wednesday to cut production but did not provide any specifics.
The ministers held a breakfast meeting ahead of the formal gathering, an unusual step pointing to a last-minute push to improve the atmosphere among the groups members who have been in disagreement since Algiers.
Abhishek Deshpande, analyst at Natixis, said: A deal now looks more likely, but there are still obstacles to overcome in the meeting.
