UPDATE 1-Mirant halts share buyback, shares tumble

(Updates from brief, adds details)

NEW YORK, Sept 22 (Reuters) - Mirant Corp (MIR.N) halted its share buyback program to ensure that it has sufficient funds to build new generating plants, the power producer said on Monday, sending its shares down 11 percent.

"We want to ensure that we have funds for the required capital expenditures and for other requirements of the business, even if turmoil in the credit markets continues and commodity prices are depressed," said Chief Executive Edward Muller, adding that the company has no liquidity issues.

Last week, Constellation Energy Group (CEG.N) agreed to sell itself to a unit of Warren Buffett's Berkshire Hathaway Inc (BRKa.N) (BRKb.N) for about $4.7 billion after investor fears about its liquidity cut its value by nearly 60 percent.

Mirant, which emerged from bankruptcy in 2006, decided last year not to sell itself and instead announced that it would buyback $4.6 billion of it shares.

Since November 2007, Mirant has bought about 110 million of its shares for $3.86 billion. (Reporting by Euan Rocha; Editing by Derek Caney)