(Fixes typo in third para)
* Market debates if Saudis will no longer defend oil prices
* Private briefings, long Naimi silence puzzle OPEC experts
* Conspiracy theories abound about what Riyadh is up to
By Dmitry Zhdannikov and Alex Lawler
LONDON, Nov 18 (Reuters) - If Saudi Oil Minister Ali al Naimi wants to stop conspiracy theories spreading before a crucial OPEC meeting next week, it's too late.
Naimi's intervention last week after a two-month silence failed to address a question energy markets want answered: is the OPEC leader no longer willing to defend oil prices which have dived by a third to their lowest since 2010, and is it pursuing new commercial or even geopolitical goals?
Despite Naimi's insistance that Riyadh wants stable markets, diplomatic and market sources say Saudi officials told recent private briefings that the kingdom can live for some time with current, or even lower, levels.
Reading Saudi oil policies has long been like Kremlinology - understanding the politics of that other secretive power, Russia. The next OPEC meeting on Nov. 27 is taking this art to a new, higher level.
A number of explanations have been offered to fill the information vacuum on Riyadh's intentions and they aren't all from the usual conspiracy theorists in Russia and Iran, which are at loggerheads with the kingdom.
Oil market watchers are divided on the outcome of the meeting in Vienna. Predictions range from a large OPEC production cut to revive prices through a small cut to none at all.
Even those who have known Naimi for decades are puzzled. "For the first time, I really do not know what is likely to happen at the meeting. It is not clear," said a long-serving senior OPEC delegate.
When Naimi finally spoke on Nov. 12, he said Riyadh's desire for stable markets had not changed. "Saudi oil policy... have been subject a great deal of wild and inaccurate conjecture in recent weeks. We do not seek to politicise oil ... For us it's a question of supply and demand, it's purely business," he said.
According to four market and diplomatic sources, who asked not to be named, Saudi officials briefed OPEC watchers privately in New York and Riyadh in September and October.
Nasser al-Dossary, Saudi Arabia's national representative to OPEC, Naimi's deputy Prince Abdulaziz bin Salman and the kingdom's OPEC governor Mohammed Al-Madhi attended at least one of these meeting to give the message that, with its large currency reserves, the kingdom was prepared to withstand oil prices as low as $70-$80 per barrel for up to a year.
Benchmark Brent crude oil slipped to $79 on Tuesday.
Most members of the cartel apart from Saudi Arabia need much higher prices to balance their budgets but ironically are unable or unwilling to reduce their output to counter a global glut caused by slowing economic growth in China and Europe, just as U.S. oil production booms.
Should the Saudis tell fellow OPEC members, badly suffering from the oil price collapse, that they will not cut output, debate will intensify on what prompted the policy shift.
One possibility is Riyadh wants to see off U.S. shale oil, which is believed to need much higher prices than conventional production to remain competitive. "They are after U.S. shale," said one participant in the meetings with Saudi officials.
However, the source added that the Saudis might also regard low prices as an opportunity to put even more pressure on Iran and Russia for supporting Syrian President Bashar al-Assad, an arch-enemy of Riyadh, in the country's civil war.
Several Saudi oil sources have denied over the past month that geopolitics are now driving the policy, but they have failed to stifle theories that Riyadh and Washington are working together to hold down prices.
"What is the reason for the United States and some U.S. allies wanting to drive down the price of oil? To harm Russia," Nicolas Maduro, president of fellow OPEC member Venezuela, said last month.
Masoud Mirkazemi, an Iranian lawmaker and former oil minister, said Riyadh was helping the G20 group of major economies. "Saudi Arabia, which intends to manage OPEC, serves the interests of the G20 group," he said.
In Russia, the idea of a Saudi-U.S. plot against Moscow has become common currency as the economy struggles under the effects of low oil prices and Western sanctions imposed over its annexation of Crimea and support for rebels in eastern Ukraine.
Leonid Fedun, a co-owner of private oil firm Lukoil, cited President Barack Obama's visit to Riyadh in March. "Obama travelled to meet the king of Saudi Arabia just after the Crimea events to push him to these actions (to lower the oil price)," Fedun, whose firm has large U.S. assets, said last month.
Russia and Iran routinely allege U.S. plots against their economies, but the conspiracy theories are spreading.
"Is it just my imagination or is there a global oil war underway pitting the United States and Saudi Arabia on one side against Russia and Iran on the other?" New York Times columnist Thomas Friedman, wrote last month.
U.S. Secretary of State John Kerry sidestepped the issue after a trip to Saudi Arabia in September. Asked if past discussions with Riyadh had touched on Russia's need for oil above $100 to balance its budget, he smiled and said: "They (Saudis) are very, very well aware of their ability to have an impact on global oil prices." (Additional reporting by Vladimir Soldatkin, Katya Golubkova, Jason Szep and Rania El Gamal; editing by David Stamp)