The U.S. Treasury Department agreed to sell $5 billion of shares in American International Group Inc. in a stock offering, with the bailed-out insurer buying $2 billion of the total, Bloomberg News reported today. The Treasury is selling 163.9 million shares at $30.50 each, compared with the May 4 closing price of $32.83, the department said. The transaction, the government's third offering of AIG's shares since last May, reduces the Treasury’s stake in the insurer to 63 percent from 70 percent.