Giant Mexican telco America Movil and broadcaster Televisa, the two companies likely to be most affected by the countrys telecoms reform, said on Thursday the regulator has told them it was determining whether they are dominant players in the sector. The notifications are the first step in a process mandated by a telecoms reform passed by Mexicos Congress earlier this year that gives the new Federal Telecommunications Institute (IFT) powers to clamp down on dominant players and spur competition. America Movil, the telecoms behemoth controlled by Mexican billionaire Carlos Slim, later said that it and its subsidiaries, including fixed-line operator Telmex, have also been placed under review by the watchdog and asked to hand over information about the size of the market. America Movil said it had received a notice related to the beginning of a process toward the probable determination of being a dominant economic agent in Mexicos telecommunications market.