First Niagara ( FNFG) plans to sell about $300 million of common stock in a public offering and use the proceeds, in part, to repay $184 million in preferred stock issued to the Treasury Department under the government's capital purchase program.

In a statement Monday, First Niagara said it also intends to use the net proceeds from the offering to "enhance its strong capital levels" in anticipation of the closing of its acquisition of $4.2 billion in deposits and 57 former National City branches from PNC Financial ( PNC).

The bank announced last week it expects the deal with PNC to close in September and boost earnings per share by 20% next year.

The bank also reported Monday first-quarter earnings of $18.7 million, or 14 cents a share, compared with $18.8 million, or 18 cents a share, a year earlier.