"When we brought together 24 producing countries in December of last year for declaration of cooperation, we made it very clear that it was still open to other producers who might want to join in this voluntary noble initiative to restore stability to the market," he told reporters here.
Saudi Arabia and Russia, he said, are leading the initiative to bring in more producers. "It is still work in progress," he added.
Last year, the bloc and some others producers decided to reduce production by around 1.2 million barrels per day from January 1, 2017. But US production has soared by almost 10 per cent this year, driven largely by shale drillers.
"I would like to invite prospective candidates, producers to join this global effort in order not only to restore the stability that had eluded this market for three years, but how to sustain it going forward. The more, the better for the industry as well as global economy," he said.
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"We had our exploratory meetings to explore areas of common interest. We were both pleasantly surprised with the outcome and the call by independents themselves that we need to continue this interaction and we are looking forward to reconvening these meetings with them shortly," he said.
Barkindo further said the shale producers in North America have been urged to "take this shared responsibility with all seriousness it deserves, as one of the key lessons learnt from the current unique supply-driven cycle".
Declining to say what price of oil would the OPEC consider as an equilibrium price that restores market stability, he quipped that equilibrium is a function of supply and demand.
The OPEC is trying to address "one variable that has been out of work since 2014", he said. "To balance the equation, you need this variable to come back to normalcy. That variable remains stocks overhang."
In the last 3-4 months, very massive de-stocking is going on, he said. "The market structure has switched to backward making it uneconomic to continue to keep storage. We are satisfied with the pace and level of the rebalancing process," he added.