The "Financial Times" estimated that the deal would be worth around $30 billion.
The merger agreement -- confirmed by several sources -- is expected to be finalized by early October.
RusAl, Sual, and Glencore all declined to comment.
RusAl is owned by 38-year-old Oleg Deripaska, Russia's sixth-richest man with a fortune estimated by "Forbes" magazine at $9 billion.
Reports say Deripaska is likely to have received President Vladimir Putin's blessing for the deal to go ahead.
Putin has been using Russia's vast natural resources to reassert Russia's power internationally.
("Financial Times," Reuters, AFP)