UPDATE 6-Saudis and Russia agree oil output freeze, Iran still an obstacle
* Saudi Arabia, Russia, Qatar and Venezuela agree plan
* Naimi says output freeze at January levels is adequate step
* Deal contingent on other producers agreeing to participate
* Iran could be obstacle, but may be offered special terms (Adds Iraq ready to freeze, Russian comments, updates prices)
By Rania El Gamal and Tom Finn
DOHA, Feb 16 (Reuters) - Top oil exporters Russia and Saudi Arabia agreed on Tuesday to freeze output levels but said the deal was contingent on other producers joining in - a major sticking point with Iran absent from the talks and determined to raise production.
The Saudi, Russian, Qatari and Venezuelan oil ministers announced the proposal after a previously undisclosed meeting in Doha. It could become the first joint OPEC and non-OPEC deal in 15 years, aimed at tackling a growing oversupply of crude and helping prices recover from their lowest in over a decade.
Saudi Oil Minister Ali al-Naimi said freezing production at January levels - near record highs - was an adequate measure and he hoped other producers would adopt the plan. Venezuelan Oil Minister Eulogio Del Pino said more talks would take place with Iran and Iraq on Wednesday in Tehran.
"The reason we agreed to a potential freeze of production is simple: it is the beginning of a process which we will assess in the next few months and decide if we need other steps to stabilise and improve the market," Naimi told reporters. Continuación...