* Rusal rejects Norilsk's $12.8 bln offer for 20 pct stake
* Focus turns to March 11 EGM (Changes sourcing)
MOSCOW, March 3 The board of Russian aluminium giant RUSAL (0486.HK) rejected on Thursday Norilsk Nickel's (GMKN.MM) offer to buy 20 percent of its shares, sources close to RUSAL board told Reuters.
Last month, Norilsk offered to buy 20 percent of its shares from RUSAL for $12.8 billion, which would leave the aluminium giant -- majority owned by entrepreneur Oleg Deripaska -- with a 5 percent stake. The deadline for the offer is March 4.
Norilsk Nickel and RUSAL could not be reached for immediate comment.
RUSAL's decision to keep the stake means the fight for control of Norilsk Nickel between entrepreneurs Deripaska and Vladimir Potanin will continue.
The next round is set for March 11, when Norilsk Nickel will hold an EGM to elect a new board.
Deripaska controls 25 percent of the company through RUSAL, while Potanin holds roughly the same amount via his Interros investment group.
However, representatives loyal to Potanin hold a majority on the current board, allowing them to control the strategy of the world's largest nickel and palladium miner. (Reporting by Polina Devitt; writing by Alfred Kueppers and Andre Grenon)