Fears over winter supply shortages have kept prices high for the best part of a month since OPEC in late September announced it would cut supply from November. The OPEC basket of crude has remained above the organisation's $22-28 optimum price band for more than a week, and several members have indicated that OPEC could raise supply levels if the basket price remains out of the range for 20 consecutive trading days. 'We maintain that the $25 price for the OPEC basket is the fair price for producers and consumers,' Saudi Petroleum & Mineral Resources Minister Ali Naimi told the London daily Financial Times on 21 October. 'What drove prices above $28 in the last few days is the buying by speculative funds. Are we happy with it? No, we're not. But the market is the ultimate determinant of price.'

OPEC secretary-general Alvaro Silva has been more cautious than other ministers, however, saying any new decision on output is unlikely until the next meeting of oil ministers on 4 December. 'The band is not as automatic as people think. The conference must activate it,' he said on 21 October. 'The cut is only enacted from 1 November so until December is only one month. We need to observe what is happening in the market and take the right decision. We need to wait until the next conference.'