AT&T said that its board approved the repurchase of up to 300 million shares, or about 5 percent of the phone company's outstanding stock and worth $11.1 billion at Friday's closing price.
The company said there was no expiration date for the authorization.
The new authorization would be in addition to the 300-million-share buyback approved by the board in December 2010. Through June 30, the nation's biggest telecommunications company had spent $4.6 billion to buy back 143.5 million of shares under the 2010 authorization.
During regular trading, AT&T's shares rose 84 cents, or 2.3 percent, to close at $37.14. During the session, they hit a 52-week high of $37.35. They were up another 41 cents to $37.55 in extended trading.
On Tuesday, AT&T reported that its net income rose 9 percent to $3.9 billion, or 66 cents per share, beating analysts' forecast by 3 cents per share.
The Dallas company was helped by the highest profit ever in its wireless division, in part because customers are hanging on to their smartphones longer. That helps reduce the amount AT&T spends to subsidize the price of new phones.
The company reported $2.15 billion in cash and cash equivalents as of June 30.
AT&T competes with Verizon Wireless, which has more subscribers and is expanding its base faster. In the second quarter, Verizon Wireless added 888,000 subscribers to 320,000 for AT&T.
In announcing the latest share-repurchase plan, Chairman and CEO Randall Stephenson said the company could return cash to shareholders through dividends and buybacks while still maintaining a strong balance sheet.