Russia exported more than 21 million tons of oil to Belarus last year, but only 5-6 million tons was for domestic consumption. The rest was re-exported, some after passing through one of the country's two oil refineries.
"The volume of oil that Russia supplies to Belarus duty-free, was calculated, and it is determined by internal needs of Belarus," Sergei Naryshkin said at a meeting with Belarusian media.
"I suggest that if the Belarusian side proves that the internal needs of Belarus in oil consumption may rise in the future the Russian side may be willing to increase tax-free delivery, but proof must be conclusive," he added.
The introduction of oil export duties forced Belarus to halve crude oil exports in the first half of 2010. Export of petroleum products has lowered by 40 percent, and the output of Belarus's oil industry by 30 percent.
Belarusian President Alexander Lukashenko has pledged to seek alternatives to Russian energy supplies.
The CIS Economic Court ruled on September 7 that Moscow and Minsk must come to an out of court agreement to their dispute over export duties.
The court dismissed a request from Belarus that Russia be prohibited from levying export duties on oil products until the end of the dispute.
