Iran, the number two oil producer in OPEC, says the cartel is likely to cut back further on production if the latest reduction does not stabilise crude prices.

The Organisation of Petroleum Exporting Countries, which produces 40 per cent of world crude, decided on Friday to reduce its production quota by 1.5 million barrels per day as of November 1 to a level of 27.3 million bpd.

Despite the announcement, the price of Brent North Sea crude sank to $US61, the lowest point for 17 months.

"Be assured that if (Friday's) decision is not effective on the market, the OPEC will take steps to consolidate the market and stabilise prices at its next meeting," Iran's OPEC representative Mohammad Ali Khatibi said in an interview on state television.

OPEC has said its latest decision will be reviewed at its next meeting in Oran, Algeria, on December 17.

Many analysts have questioned the effectiveness of measures taken by OPEC, given the seriousness of the global financial crisis that has sharply reduced the prospects for economic growth and thus oil consumption.

Crude futures in London and New York have plunged close to 60 per cent from record highs of above $US147 a barrel reached only three months ago when supply concerns sent prices soaring.