Iran has threatened to stop crude oil supplies to India from next month if a mechanism to pay for imports is not found quickly. Industry official said in New Delhi that National Iranian Oil Co. has written to the Mangalore Refinery and Petrochemicals Ltd and EssarOil, who are the principal buyers of Iranian crude, demanding that a mechanism be put in place to pay for its oil supplies. Iran is supplying about 400,000 barrels per day of crude oil to India on credit since December last year when the Reserve Bank of India scrapped a long-standing mechanism to pay for import from Iran using a clearing house system run by regional central banks.Outstanding payments have gone up to $9 billion leading to the urgency to find alternative mechanism.