AT&T Inc., the biggest U.S. phone company, approved a plan to repurchase 300 million shares, or about 6 percent of its outstanding stock.

The authorization, which has no expiration date, gives Dallas-based AT&T a total of 425 million shares it’s permitted to buy back, according to a statement today. The company has acquired 775 million shares since 2012.

AT&T is giving itself room to boost shareholder returns while Chief Executive Officer Randall Stephenson considers whether to go after acquisitions in Europe or the U.S. The company said it expects to maintain its ratio of net debt to adjusted earnings at 1.8 or lower, compared with 1.73 at the end of 2013.

AT&T climbed less than 1 percent to $35.37 at 9:45 a.m. in New York. At that price, repurchasing 300 million shares would cost about $10.6 billion.