Oil prices rose on Monday, supported by concerns that falling Iranian output will tighten markets once US sanctions bite from November, but gains were limited by higher supply from OPEC and the United States, reports Reuters.
Brent crude oil was up 45 cents at $78.09 a barrel by 1045 GMT. US crude was 10 cents higher at $69.90.
The two benchmarks have risen strongly over the last two weeks with Brent gaining more than 10 per cent on expectations that global supply will tighten later this year.
US sanctions are already curbing exports from Iran.
"Exports from OPEC's third-biggest producer are falling faster than expected and worse is to come ahead of a looming second wave of US sanctions," said Stephen Brennock, analyst at London brokerage PVM Oil Associates. "Fears of an impending supply crunch are gaining traction."
Stephen Innes, head of trading for Asia-Pacific at brokerage OANDA, said Brent was "supported by the notion that U.S. sanctions on Iranian crude oil exports will eventually lead to constricted markets".
Edward Bell, analyst at Emirates NBD bank in Dubai, agreed: "Iranian production is already showing signs of decline, falling by 150,000 bpd last month ... (as) importers of Iranian barrels will already be moving away from taking shipments."
But global oil markets are still fairly well supplied.
Production by the Organization of the Petroleum Exporting Countries rose 220,000 barrels per day (bpd) in August to a 2018 high of 32.79 million bpd, a Reuters survey showed.
Output was boosted by a recovery in Libyan production and as Iraq's southern exports hit a record high.
US drillers added oil rigs for the first time in three weeks, increasing the rig count by 2 to 862. The high rig count has helped lift US crude production by more than 30 per cent since mid-2016 to 11 million bpd.