Western sanctions have strained Russian oil company Rosneft's ventures and relations with ExxonMobil, as well as with Halliburton and Norwegian oil company NADL, Artur Chilingarov, a member of  Rosneft's board of directors, said.

The sanctions imposed by the U.S. caused ExxonMobil to suspend nine of 10 projects with Rosneft last month, including drilling at the Universitetskaya-1 well in the Kara Sea.

“In current conditions, further cooperation with these companies is complicated,” Chilingarov said.