Japan's Toshiba Corp <6502.T> plans to bid for French nuclear group Areva's power distribution and transmission equipment unit in a deal that could cost it more than 500 billion yen ($5.4 billion), industry sources said.

Toshiba shares slid after news broke of the planned bid, which would put it up against a range of potential suitors including Alstom and Schneider Electric .

Areva, a state-controlled nuclear reactor maker, has put the unit up for sale, and French Economy Minister Christine Lagarde said this week she hoped the firm would reach a decision on the possible sale by the end of 2009.

Officials of Toshiba were not immediately available for comment on the potential bid, for the unit, which is No.3 in its field after ABB and Siemens .

($1=92.56 Yen)

(Reporting by Taiga Uranaka)

Japan