(Adds background, share price)
MEXICO CITY, June 30 (Reuters) - AT&T Inc said on Monday it had sold its equity in America Movil for $5.57 billion to a company controlled by Carlos Slim, allowing the billionaire to tighten his grip on the giant Mexican telecoms company.
On Friday, Slim's real estate company Inmobiliaria Carso announced it was going to buy the stock, which AT&T said in May it would sell to help it gain regulatory approval for its purchase of DirecTV.
The stock purchase gives Slim even more control over America Movil, his principal cash cow. Slim's firms and family already control more than 50 percent of America Movil's voting stock.
AT&T said in a filing it sold the stock comprising 72.8 million "L" shares and 5.74 billion "AA" shares, which do not regularly trade.
America Movil shares closed up 1.2 percent at 13.45 pesos ($1.04) per share.
$1 = 12.9707 Pesos Writing by Gabriel Stargardter; Editing by Dave Graham and Lisa Shumaker