News of the talks on Sunday helped offset downward pressure on oil prices amid worries that energy demand would be hit hard by Hurricane Irma and its aftermath. More recently Hurricane Irma left more than seven million homes without electricity in Florida. By Monday morning, it had weakened to a tropical storm, heading towards Georgia.
Global benchmark Brent crude futures, the benchmark for oil prices outside the USA, fell 0.30% to $53.62 a barrel.
Worldwide benchmark Brent crude edged 32 cents higher to $54.16 per barrel by 1235 GMT from the previous close.
The 14-country producer group said its oil output in August fell by 79,000 barrels per day (bpd) from July to 32.76 million bpd, below a demand forecast.
US crude stockpiles likely rose by 4.82 million barrels last week, according to a Bloomberg survey ahead of Energy Information Administration data released Wednesday.
Saudi Arabia-OPEC's most influential member-has been debating whether to extend the cartel's production accord after it expires in March 2018.
The week will also see key monthly reports from the Organization of Petroleum Exporting Counties and the International Energy Agency to assess global oil supply and demand levels.
"Crude oil output increased in Nigeria, while production showed declines in Libya, Gabon, Venezuela and Iraq", the report said.
Non-Opec Kazakhstan is aiming for a stand-alone deal with Opec on restraining its crude production due to a need to crank up output at its Kashagan field, a Kazakh official said last week.
"By the end of this month, we expect crude stocks to be 43 million barrels higher than they would have been had Harvey and Irma not occurred", analysts at Goldman Sachs said in a note.
The deal agreed late previous year helped to keep prices as high as $58 a barrel in January, but they have since sagged as global stocks have not fallen as quickly as expected.
Meanwhile, U.S. President Donald Trump said North Korea would regret escalating recent nuclear tensions, but added that a military option wasn't inevitable.
After Hurricane Harvey halted nearly a quarter of the nation's refining capacity, crude prices in NY slumped as gasoline prices soared.
The news comes on the heels of a statement from Riyadh that Oil Minister Khalid al-Falih had discussed the possibility of another extension of the 1.8-million bpd production agreement between OPEC and 11 other producers beyond the March 2018 deadline.