(Adds comments from analysts, details on regulatory issues)
MEXICO CITY, July 18 (Reuters) - America Movil, Latin America's largest telecommunications company by number of subscribers, posted an 86 percent increase in net profit in its second quarter, helped by the peso's gains.
The company, controlled by the family of Mexican billionaire Carlos Slim, reported net profit of 14.3 billion pesos, or $788.9 million, compared with 7.7 billion pesos in the year-ago quarter.
America Movil pointed to a 21.8 percent increase in mobile data revenues as a key driver of its success.
"At constant exchange rates, service revenues were up 4.2 percent year-on-year, their best performance in ten quarters," the company said in a release accompanying its earnings.
The company has reaped strong mobile gains across the board, said Intercam analyst Alik Garcia.
"Not only in Mexico but in the rest of the countries (where America Movil operates), it has been an important differentiator," he said.
The company's quarterly performance fell short of expectations for a profit of 21.7 billion pesos forecast by a Reuters poll last week.
Analysts had expected America Movil to get a boost from the Mexican peso's recent rally. The peso appreciated nearly 3.9 percent in the second quarter, according to Reuters data.
The company generated revenue of 249 billion pesos for the quarter, up from 233 billion pesos in the same three-month period last year.
America Movil is still recovering from a 2013 reform of the telecom sector intended to lessen its dominance, which sharply lowered prices for Mexican consumers.
In March, the Federal Telecommunications Institute (IFT) imposed new antitrust measures against America Movil, forcing it to separate part of its network infrastructure into a new entity.
But the Supreme Court is currently considering whether to wipe away parts of the reform that tilted the playing field against America Movil, and a ruling could come as soon as August.
America Movil's lawyers maintain that legislators did not have the right to create "asymmetrical" rules meant to help smaller players.
Nevertheless, America Movil appears to have adjusted to the new regulatory landscape, said Carlos de Legarreta, an analyst at GBM.
"There's been a number of regulatory measures and subsequent competition increase both in wireless and fixed segment," de Legarreta said.
America Movil's shares closed up 0.47 percent at 15.04 pesos on Tuesday before the reports release. The stock has been trading around a two-year high.
($1 = 18.143 Mexican pesos on June 30) (Reporting by Julia Love; additional reporting by Sheky Espejo in Mexico City; Editing by Diane Craft and Sandra Maler)