The Paris-based agency said Opec supply restraint that has succeeded in raising prices from recent 22-year lows would remove the equivalent of 1.6 million barrels per day from the world's inventories of unwanted oil. "A stockdraw of that magnitude is unusual, especially in the third quarter, when stocks have been built up in 12 of the last 14 years," the agency said in its Monthly Oil Market Report.

The agency, the West's energy watchdog, said an even larger 3.2 million bpd stock draw would result in the fourth quarter of the year if restraint by the 11-member Organisation of petroleum Exporting Countries and a handful of other producers remained good.

But it said such a large draw was unlikely because strengthening markets would tempt producers to increase production, resulting in anappreciable increase in supply. OPEC has set itself an $18-$20 a barrel target range for benchmark Brent crude which on Monday broke above $18 for the first time since December 1997.