U.S. and Western officials are finalizing plans to cap Russian oil prices amid a World Bank warning that such a plan would require the active participation of emerging market countries to be effective, Reuters reports.

Officials said the price range had not yet been determined, but one source familiar with the process said the cap would be determined in line with the historical average of $63 to $64 a barrel, a level that could be a natural upper limit. That level is consistent with Treasury Secretary Janet Yellen's recent comments that a price cap in the $60 range would give Russia an incentive to keep producing oil.

President Joe Biden's administration saw the price cap as a way to reduce Russia's oil revenues while maintaining Russian oil supplies and avoiding price spikes.

The actual price will be set in the coming weeks ahead of the European embargo on Russian oil scheduled for Dec. 5 and related restrictions on offshore oil transportation and insurance.

A senior Biden administration official said the claims about any price range were incorrect, but declined to go into detail.

U.S. officials denied a Bloomberg News report that they had been forced to cut back on plans to cap prices, with fewer participating countries and higher prices.

The administration had been telling reporters for weeks that the price cap was already taking its toll, allowing countries to demand bigger discounts from Moscow.

Bloomberg also reported that South Korea has privately told G7 countries that it plans to comply, and G7 officials have also tried to get New Zealand and Norway to participate.

Earlier this month, Yellen told reporters that the coalition advocating a price cap includes the G7, the European Union and Australia.

Western diplomats say the price cap already gives India and other buyers of Russian oil more leverage in negotiations with Moscow, allowing them to get good discounts.

The World Bank said the G7 oil price cap could affect the flow of oil from Russia, but it is an untested mechanism and needs the participation of large emerging markets and developing countries to be effective. The WB recalled that Russia said it would not trade with countries participating in the price ceiling.