MOSCOW, November 20 (RIA Novosti) - The chief executive of Russia's metals giant Norilsk Nickel has asked Russian Prime Minister Vladimir Putin to repurchase a blocking stake of 25% in the company from RusAl, a business paper said on Thursday.

According to Vedomosti, Vladimir Strzhalkovsky, a longtime acquaintance of the Russian premier, raised the idea out of fears that Russia might lose control of the metals giant.

The Russian aluminum giant RusAl acquired a 25% stake in Norilsk Nickel from billionaire Mikhail Prokhorov in April this year, taking a syndicated loan from 11 Western banks, and pledging the stake as collateral, Vedomosti said.

Norilsk Nickel's stock has depreciated by about 80% since then amid the credit market crisis and falling nickel prices, while RusAl was obliged in late October to provide additional security to the banks. A sum as large as $6 billion was mentioned, the paper reported.

In this situation, 25% of Norilsk Nickel shares could pass over to foreign control while a larger part of the metal giant's stock is held by minority shareholders in the form of American Depositary Receipts (ADRs), the paper said.

"In this connection, I have applied to the government leadership [with a statement] regarding the danger of the current situation and with a request that VEB [Vnesheconombank] repurchase this package," the paper quoted Strzhalkovsky as saying.

In late October, Vnesheconombank granted RusAl a $4.5 billion loan to repay liabilities to Western banks.

However, analysts say the threat of losing a stake in Norilsk Nickel still exists for RusAl as VEB only granted the metals giant a twelve-month loan and the situation is unlikely to improve significantly in 2009, the paper reported.