Wells Fargo & Co. has informed that it will sell at least $10 billion worth of common stock in a public offering, to fund its acquisition of east-coast lender Wachovia.

The San Francisco-based bank previously said it would raise up to $20bn of capital, primarily common equity, to fund the $15bn all-stock acquisition.

Wells Fargo expects to complete buyout of Charlotte, North Carolina-based Wachovia by fiscal end. The purchase would more than double Wells Fargo's size, creating a bank with $1.4 trillion of assets and 6,653 banking offices across the country.

Post acquisition, Well Fargo will become the fourth-largest US bank by assets. Last month, Wells sold $ 25 billion of preferred shares to the US government in October, as it’s required to do under the U.S. Treasury’s program to invest directly in the nation’s banks.

J.P. Morgan Securities Inc. is serving as lead manager on the deal. Goldman Sachs & Co, Morgan Stanley, UBS and Wachovia Securities are joint book runners.

Recently, Wells Fargo's board made exclusion to its compulsory retirement age of 65 to let Dick Kovacevich remain chairman throughout the integration process.

Wells Fargo shares drops nearly 10 percent to close at $31.68 on Wednesday. The scrip during trading hours has touched an intraday high and low of $ 35.00 and $31.31.