Scepticism about any deal being reached has prompted money managers to cut their bullish bets to a one-month low last week, when prices fell by nearly 5%.
Opec members are meeting informally on the sidelines of the International Energy Forum in Algeria from 26 to 28 September, where they will discuss a possible deal to limit output.
Iran, which is still ramping up production to where it was in 2012, before the imposition of Western sanctions that lifted in January, downplayed the chances of a deal, although several other members of the group said they still hoped there would be some agreement on how to tackle a global surplus of oil.
Brent
