Exelon Corp., Peco's parent company and the nation's largest nuclear power generator, said today that it has sent a letter to NRG Energy Inc. stockholders urging them to support Exelon's takeover bid.

Chicago-based Exelon, in a Securities and Exchange Commission filing, said it is urging stockholders of Princeton-based NRG to vote at their Aug. 21 annual meeting in favor of proposals to replace NRG's board of directors with nine new members.

Exelon is attempting to take over NRG in a $5 billion deal that would create the nation's largest power generator. NRG has resisted Exelon's overtures, saying the offer undervalues the company.

John W. Rowe, Exelon's chairman and chief executive, said in the letter that a combined Exelon and NRG represents compelling and substantial value for NRG stockholders.

"We also believe that the quickest and clearest path for NRG stockholders to realize the benefits of a transaction with Exelon - or any other strategic transaction - is to elect directors to the NRG board who are not entrenched in their opposition to a transaction," Rowe wrote.

Exelon shares fell 63cents, to $48.30 in morning trading, while NRG dropped 27 cents, to $22.63.