President Enrique Pena Nieto enacted a law Monday that aims to open up Mexico's telecommunications industry to competition.
The Congress approved the enabling legislation on Wednesday, hours after telecoms giant America Movil, owned by billionaire Carlos Slim, announced plans to shed its dominant share of the country's telephone phone market.
At a ceremony at the national palace, Pena Nieto said the new law "fosters competition, productivity and innovation."
America Movil currently has an 80 percent share of the traditional telephone market, and holds 70 percent of the mobile phone market.
Its market share must drop below 50 percent to meet the requirements of the new law.
Televisa, the other major telecom affected by the law, has a 70 percent share of the broadcast TV market and 60 percent of the cable TV market in Mexico.