Ministers from The Organization of the Petroleum Exporting Countries, Russia and their allies, known as OPEC+, are due to gather online at 1300 GMT. An OPEC+ ministerial panel that monitors market developments, known as JMMC, meets before that.

Benchmark Brent crude , up 50% so far this year, surged above $80 a barrel last month and was trading around $79 on Monday, pushed up by supply disruptions and surging demand as the global economy recovers from the COVID-19 pandemic.

The group agreed in July to boost output by 400,000 barrels per day (bpd) every month until at least April 2022 to phase out 5.8 million bpd of existing cuts.

"The most reasonable is to add 400,000 bpd, no more," one of the sources told Reuters when asked about what ministers were expected to decide. Another also said this was the most likely outcome, but left room for a possible increase.

Last week, OPEC+ sources had said producers were considering adding more than the deal envisaged, but none had given details on how much more or suggested any timing.

OPEC+'s last meeting decided the October volumes.

Iraqi Oil Minister Ihsan Abdul Jabbar said on Sunday that oil prices at $100 a barrel would not be sustainable and said OPEC wanted stable markets.

A senior aide to U.S. President Joe Biden met Saudi Crown Prince Mohammed bin Salman in Saudi Arabia last week to discuss the war in Yemen but said oil was also "of concern". India, another big oil consumer, has been pushing for more supply.

In a note published on Friday, JP Morgan analysts said: "Considering the declining refinery runs and weakening physical market indicators in China we do not see the incentive for the OPEC+ alliance to boost oil production beyond the currently-committed 400,000 bpd."

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