Iran has warned it will stop crude oil supplies to India from August if its long-pending bills aren't cleared and a favorable mechanism for future payments isn't evolved, executives at two Indian refiners said Friday. "We have got the letter from National Iranian Oil Co. They are saying supplies can be halted," an executive at Mangalore Refinery & Petrochemicals Ltd., who didn't wish to be named, told Dow Jones Newswires

Iran has warned it will stop crude oil supplies to India from August if its long-pending bills aren't cleared and a favorable mechanism for future payments isn't evolved, executives at two Indian refiners said Friday.

"We have got the letter from National Iranian Oil Co. They are saying supplies can be halted," an executive at Mangalore Refinery & Petrochemicals Ltd., who didn't wish to be named, told Dow Jones Newswires.

Executives at NIOC couldn't be reached for comment and didn't respond to e-mailed requests for comment.

Iran is the second-largest crude supplier to India after Saudi Arabia, accounting for about 13%-14% of the country's oil imports. Refiners including Indian Oil Corp. Ltd. (530965.BY), Hindustan Petroleum Corp. Ltd. and MRPL use Iranian crude.

India and Iran are trying to negotiate a new payment mechanism after the Reserve Bank of India in December stopped trade-related payments through the Asian Clearing Union, which the U.S. says is opaque and could be used by Tehran to finance its alleged nuclear weapons program.

An executive at Hindustan Petroleum, who also didn't wish to be named, said the payments are being lined up by the Reserve Bank of India and will be made shortly. "The supplies are continuing and I don't see any threat," he said.

Indian Oil Finance Director P.K. Goyal and Bharat Petroleum Corp. Ltd. (500547.BY) Chairman R.K. Singh said they weren't aware of any letter from Iran on August crude supplies.

On May 31 India said it will continue discussions with Iran on crude oil payment settlements after two days of talks between officials from both countries on ending an impasse over payments proved inconclusive.

Indian refiners owe Iran $2 billion towards crude oil payments, NIOC Executive Director Seyed Mohsen Ghamsari said in May after meetings with Indian officials.

"This has happened for the first time... They look to be pressuring the Indian government to quickly resolve the payment issue," an Indian trader with a state-run oil firm said.

Traders and industry executives say Iran won't stop exports to Asia's third-largest economy as it needs an outlet for its oil when the number of companies it can deal with is gradually shrinking because of the West's sanctions on Tehran over its nuclear program.

Iran, which has been supplying oil to Indian refiners on credit since the start of this year, may find it difficult to place its crude elsewhere at a time when Saudi Arabia is boosting its oil output after an Organization of Petroleum Exporting Countries meeting earlier last month failed to agree on raising its output quota.