Oil prices have dropped due to doubts that prominent oil producing countries will cut production.
Brent crude futures LCOc1 were down 35 cents and traded at $51.58 per barrel, while the US West Texas Intermediate (WTI) futures CLc1 dropped 39 cents at $49.42 a barrel, Reuters reported.
OPEC is planning to agree on an output cut when it is set to meet in late-November this year.
Major oil producers are targeting production cut to a range of 32.50 million barrels per day (bpd) to 33 million bpd.
At present, OPEC is producing 33.6 million bpd.
Morgan Stanley told the news agency: "A meeting between OPEC and non-OPEC producers (namely Russia) will add to oil headlines this week. Don't expect a firm agreement from Russia, but headlines about cooperation are likely."
The bank further added that oil ministers from Iraq and Iran will not participate in the meeting.
A Reuters poll revealed that even if a deal is agreed by the producers, it may lead to much higher prices as the announced reductions are not deep.
Adding to these pressures, Iraq said it plans to increase production next year.