HOUSTON (AP) — Russian oil company Rosneft is buying a 30 percent share of 20 exploration blocks held by ExxonMobil in the deep waters of the Gulf of Mexico.

Exxon will retain a 70 percent stake in each block and remain the operator. Rosneft received an option to acquire minority stakes in some of Exxon’s Gulf fields when the two signed an exploration agreement in Russia last year.