Shares in Latin American telecoms giant America Movil fell 4 percent to a year low on Friday after Mexican regulators said that new rules aimed at curbing the operator’s dominance in the country could be introduced as early as this month. Mexico’s Federal Telecommunications Commission plans later this month to apply restrictions to America Movil’s fixed-line unit in the market for leasing lines to rivals, Mony de Swaan, the agency’s president, told Bloomberg last week. New rules governing its mobile arm are set to follow. “They’re decisions that can greatly impact the market, so we want to tread carefully,” said de Swaan. “It will be a mix of different measures having to do with fees, information and quality.” The new rules will be based on recent findings by Mexico’s antitrust agency that identified America Movil’s dominance and gave the green light to de Swaan’s agency to target the operator with specific regulation. America Movil is challenging the antitrust findings.

America Movil controls 70 percent of Mexico’s mobile market, while its fixed-line unit – known as Telmex – has 80 percent of the country’s fixed-lines and about 70 percent of its Internet connections. The regulator’s most likely plan to remedy the situation with regards to mobile will be to reduce interconnection rates further; it has already reduced the rate by half this year. As the largest player, America Movil is deemed to benefit the most from interconnection fees. According to Bloomberg, America Movil’s stock dropped MXN1.2 to MXN28.73 (US$2.5) on Friday, its biggest decline since June 2010, and to its lowest price since March 2010.