June 23 (Bloomberg) -- Iranian supertankers now in the Persian Gulf could store the equivalent of five months worth of the additional crude oil Saudi Arabia pledged to pump to curb prices, according to ship-tracking data compiled by Bloomberg.

Saudi Arabia said it would increase production by 200,000 barrels a day in July, after a summit of leading oil producers and consumers in Jeddah yesterday. Saudi Arabia and Iran are the OPEC's two largest oil producers.

Iran has 13 to 15 supertankers idling in the Gulf with capacity to hold as much as 30 million barrels, the ship-tracking data shows. Iran has not said how much oil is in the tankers. Hojatollah Ghanimifard, executive director of international affairs at National Iranian Oil Co., said June 2 that some vessels were storing crude while refineries carried out annual repairs.

The chart of the day lists 16 Iranian ships, of which 13 are idling either at the country's Kharg Island oil loading facility or the nearby Soroosh Terminal, according to AISLive data on Bloomberg. The signals of two other vessels at the facilities were tracked last week. Each supertanker has the capacity to store about 2 million barrels of crude.

Ghanimifard said that the ``number of vessels will decrease by the end of June,'' as refineries that can process Iran's sulfur-rich crude reopen after maintenance.

200,000 Barrel Increase

Saudi Arabia will raise daily crude output by 200,000 barrels to 9.7 million barrels next month, Saudi Oil Minister Ali al-Naimi told officials from 35 producing and consuming countries at the summit yesterday.

OPEC President Chakib Khelil said the Saudi initiative would fail to lower prices, blaming oil's climb above $130 a barrel on speculation, rather than a lack of crude. Saudi Arabia's output increase is ``illogical'' and may do nothing to lower prices, he said after the meeting in Jeddah.

Also, if the oil is of ``poor quality,'' it would have little effect on prices, Thierry Lefrancois, a strategist with Natixis in Paris said last week.

Oil prices rallied to a record $139.89 in New York on June 16, five times the average six years ago. World oil demand will rise 800,000 barrels a day, or 0.9 percent this year, according to the International Energy Agency.

The world's leading oil consumers are also taking steps designed to stall the price of oil.

China, the second-biggest energy consumer, increased gasoline and diesel prices by as much as 18 percent on June 20. China's oil consumption will average 8.02 million barrels a day this year, the U.S. Energy Department said in a report this month.

U.S. President George W. Bush on June 18 called on Congress to lift a 27-year-old moratorium on offshore oil and gas drilling, to increase supply and lower prices.

To contact the reporters on this story: Lee J. Miller in Bangkok at lmiller@bloomberg.netAlaric Nightingale in London at Anightingal1@bloomberg.net

Last Updated: June 23, 2008 03:26 EDT