(Updates with comments from Telefonica)
By Christine Murray and Tomas Sarmiento
MEXICO CITY, April 21 (Reuters) - A Mexican court said on Monday it would begin analyzing an injunction request from telecommunications giant America Movil against a regulatory ruling designed to curb its dominance and spur competition.
Controlled by tycoon Carlos Slim, America Movil has about 80 percent of Mexico's fixed-line business and some 70 percent of the mobile sector. It was ruled dominant earlier this year by new regulator the Federal Telecommunications Institute (IFT).
That ruling allowed the IFT to impose a series of tougher regulations against Slim's flagship company. Rival phone company Telefonica said on Monday it was failing to abide by those regulations.
The court, which specializes in competition and telecoms cases, said it had admitted the injunction against the IFT.
The Federal Judicial Council, the Mexican judiciary's administrative arm, said a constitutional hearing will now take place on May 13 to hear both sides of the argument.
Mexican companies like America Movil have used injunctions to block regulator decrees for years, but a constitutional reform passed last year means that injunctions can no longer be used to suspend regulatory actions while an appeal is processed.
The court dismissed America Movil's request for an injunction against the reform itself.
Spain's Telefonica, which is a distant second to America Movil in Mexico mobile subscriber numbers with around 20 percent of the market, on Monday accused America Movil of breaking the weeks-old IFT regulations.
In a statement, Telefonica said Slim's company was failing to share its network, provide information about its infrastructure or give unblocked mobile phones to customers.
A spokeswoman for America Movil had no immediate comment. (Additional reporting by Anahi Rama; Editing by Cynthia Osterman)