The Organization of Petroleum Exporting Countries (OPEC)'s weekly average crude oil prices dropped slightly by 0.52 dollars to 54.76 U.S. dollars per barrel last week, the cartel's secretariat said on Monday.

The recent development of the international oil prices indicated that OPEC's decision on Oct. 20 to cut the output by 1.2 million barrels per day could not hold back the drop in oil prices.

After rising slightly on Oct. 20, OPEC's oil prices fell again by 1.63 dollars, the following day.

Due to doubts in the market about the actual effect of OPEC's production cut, coupled with the slow-down in the U.S. economy, market analysts believe that international oil prices would drop slowly in the short run.

According to the data issued by the U.S. Department of Commerce, in the third quarter, the economic growth in the U.S. increased only 1.6 percent, the lowest recorded growth rate in the past three years.

OPEC is scheduled to hold a ministers' conference on Dec. 14 to discuss the effect of the Oct. 20 decision on production cut.

A senior Iranian oil official said on Sunday that OPEC would seek new steps if the cut did not help stabilize prices for crude oil on the international market.