A long-discussed unified export duty on Russian oil products won't be implemented until at least August 1 due to disagreements with some refiners, for which the change will hurt profits, Russia 's Energy Ministry said Tuesday.

The proposal, known as the "60/66" tax, would cut the duty on crude oil to a marginal rate of 60%, from 65% previously, while adjusting duties on refined products to 66% of the level of crude oil. The proposal will make it more profitable to export crude oil and to refine oil into high-quality, lighter refined products.

"The energy and finance ministries have yet to solve the problem of companies for which the 60-66 regime could potentially mean a slight decrease in oil refining profitability," said Dmitry Klokov, an advisor to Energy Minister Sergei Shmatko.

"In any case, the 60-66 tax regime will take action mode no earlier than August 1," Klokov said.