State development bank VEB later said it would invest up to 111 billion roubles ($1.68 billion) in the project, whose total costs have been estimated by Gazprom at 900 billion roubles.

The Russian sovereign fund and other state banks may also provide financing.

Royal Dutch Shell quit the project earlier this year after Gazprom moved to integrate its Baltic LNG project and gas processing plants and added a partner with links to an ally of President Vladimir Putin.

"It's big and expensive," Medvedev said of the Ust-Luga project during a board meeting with state development bank VEB.

"(The project) certainly requires careful attention from the state, taking into account that this project can not kick off without it."