Oil prices slumped after 11 September
The oil cartel's president, Chakib Khelil, told Abu Dhabi television that at the 28 December talks, the 11 members will discuss oil market conditions and pledges by non-Opec producers to cut production.
Opec members are pressing for cuts in production levels to try to stop the sharp fall in prices, resulting from the drop in worldwide demand since the 11 September attacks on the United States.
The price of a barrel of the benchmark Brent crude stands at $18.40.
The cartel, which produces about 40% of the world's oil, has cut production by 3.5 million barrels a day so far this year.
Last month Opec members agreed a cut of 1.5 million barrels per day, starting in January.
But the implementation of the reductions is conditional on non-Opec nations, such as Russia, Norway, Oman and Mexico, also trimming output by 500,000 barrels per day.
'Encouraging signs'
Crude oil prices hit a 29-month low in November, and the cartel has put considerable pressure on non-member countries to co-operate in combating the price fall.
Figures: barrels per day
Non-Opec countries have pledged to cut production, but have not yet agreed on the exact amount.
Norway, Mexico and Russia were discussing production cuts on Saturday.
The 500,000 barrel target can be reached if Norway, the third largest oil exporter, agrees to reduce production by 200,000.
Russia, Mexico and Oman have between them pledged daily cuts of 275,000 barrels per day, and Angola says it is prepared to reduce output by 22,500.
Mr Khelil said the signs were encouraging and said there was a "good spirit of co-operation between Opec and non-Opec countries.