Russian Energy Minister Alexander Novak, for his part, said Thursday that the increase in shale production was expected. And, had the group of oil producers not agreed to cut supply, they "would have been even more greatly affected," he said.
Russia, along with OPEC and other non-OPEC countries, agreed on Thursday to extend productions cuts until the end of 2018.
The deal to cut oil output by 1.8 million barrels a day was adopted last winter by the 14-member OPEC cartel, Russia and nine other global producers. The initial agreement was due to end in March 2018, having already been extended once.
But global oil output is not just up to those countries: American shale drillers increased their output every month this year, with production expected to reach 6.17 million barrels per day in December, figures from the Energy Information Administration showed.
The increase in U.S. shale production and exports is seen as a threat to the pact's effort to re-balance the market. Rising oil prices, largely a result of the group's supply cut, were thought to have encouraged U.S. shale producers to come back online.