OPEC's oil output dipped in August, the cartel said Tuesday, a sign that supply and demand could be moving further towards balance.

Production by the 14 members of the  Organization of the Petroleum Exporting Countries came to 32.755 millions of barrels per day (bpd) last month after 32.834 in July, it said in a report, citing secondary sources.

OPEC and a number of other producers including Russia agreed in May to extend production cuts, originally agreed last year, into 2018 to ease a global supply glut and support the price of crude.

In August, production rose in Nigeria, which has been exempted from output curbs, OPEC said.

It fell in Libya, also exempt, and in Venezuela as both countries struggle with political trouble. Output also dropped in Iraq.

"It is clear that the rebalancing process is underway, supported by the high conformity levels of OPEC member countries and participating non-OPEC countries to the production adjustments" in the cooperation agreement, OPEC secretary general Sanusi Barkindo said in a speech in Oxford on Monday.

OPEC meanwhile revised upwards its estimate for global oil demand by 1.42 million bpd to 96.77 million bpd this year. Demand is expected to rise by another 1.35 million bpd in 2018 as developed countries consume more oil than initially forecast.

"Oil demand has been quite robust in 2Q17, particularly in the Americas and Europe," the report said.

Commenting on the impact on oil production of hurricane Harvey, OPEC said "the US energy industry appears to be rebounding quickly".

Nevertheless, the advent of Irma raised the possibility of a particularly destructive hurricane season this year, "with potential implications for the oil market", but OPEC promised to do its bit for the "stability and security" of the oil market.

Despite the efforts to cut output, the oil price has struggled to push durably above $50 a barrel.

On Tuesday, WTI oil futures stood at $48.22 and Brent Crude at $54.23.