Russia’s state-owned Rosneft teamed up with U.S. company ExxonMobil on Tuesday in a multibillion deal to develop offshore oil fields in the Russian Arctic — one of the last regions with immense and untapped hydrocarbon deposits — in return for access to resources in the Gulf of Mexico.

Because Rosneft does not have its own technology for deep sea drilling, it was looking for partners to develop the offshore projects in the Arctic and other regions of Russia. A deal it was pursuing with Britain’s BP earlier this year fell through, leaving the path open for ExxonMobil.