Exelon Corp., which is pursuing a hostile takeover of Princeton energy company NRG Energy Inc., said NRG shareholders had tendered 45.6 percent of the target's common shares as of yesterday.

Exelon, the Chicago-based parent of Peco Energy, said it was encouraged by the response and extended its exchange offer of 0.485 shares of Exelon stock for each share of NRG stock until at least Feb. 25.

In October, Exelon announced its bid to buy NRG in a deal valued then at $6.2 billion. NRG's board rejected the offer as being too low.

Exelon's all-stock offer valued NRG at $26.43 a share, a 37 percent premium over the closing price on Oct. 17, the last trading day before public disclosure of the offer. The offer was 44 percent lower than NRG's 52-week high of $47.19.

In a statement today, NRG said:

"Over the past few months since Exelon initiated its hostile exchange offer, we have had extensive contact with our shareholders and received considerable feedback. We take very seriously the views of our shareholders and appreciate the support that our shareholders have provided for the NRG Board's decision that the current Exelon offer is highly conditional and significantly undervalues NRG.

"As always, we remain open to being a buyer or a seller at an appropriate value that compensates for the value and risks of the transaction."

Exelon shares were down $1.45 (2.53 percent) to $55.97 in late-morning trading on the New York Stock Exchange. NRG shares were down 81 cents (3.29 percent) to $23.80.