Mitsubishi Corp will submit an agreement form to take a stake in the project by the deadline set for Sept. 4, a spokesperson said.

The move comes after the Japanese government asked Mitsubishi Corp to "think positively" in joining the new entity as the Sakhalin-2 is a key source of stable energy supply for Japan.

Russian President Vladimir Putin signed a decree in June to take charge of the Sakhalin-2 project in Russia's far east, raising the stakes in an economic war with the West and its allies.

(Reporting by Sakura Murakami; Editing by Jacqueline Wong and Muralikumar Anantharaman)