Oil rose slightly on Tuesday, boosted by dollar weakness, but gains were muted due to expectations Opec might raise its production target this week and to worries about the demand outlook.
US crude has stayed in a fairly tight range for a month as concerns that global growth would hit demand have been offset by supply worries caused by civil war in Libya and turmoil in Syria and Yemen.
Brent crude added 27 cents to $114.75 (Dh421) a barrel after reaching its weakest close in nearly two weeks on Monday. US light crude for July delivery was flat at $99.01 a barrel.
Investor eyes are now firmly fixed on this week's Opec meeting, at which major oil producers are at odds over whether to boost production quotas. Saudi Arabia and its Gulf Arab allies may struggle to push more than a cosmetic increase in oil supplies.
"Sentiment is still cloudy ahead of Opec. The only effect counteracting at the moment is the weaker dollar, which has seen a continuation of the trend from last week in the aftermath of the weaker US data," said Carsten Fritsch, an anal-yst at Commerzbank.
The dollar fell broadly to hit a one-month low against a basket of currencies and the euro and to a record low versus the Swiss franc after a Chinese official warned of the risks of excessive dollar holdings.
Top oil exporter Saudi Arabia and other Gulf producers, including Kuwait and the United Arab Emirates, favour a hike in output on concerns that high oil prices are limiting economic growth.