* Bidders must seek competition clearance from new watchdog by Jun 17 * Watchdog must respond by Sept 9 * Process part of bid to boost competition in telecoms sector MEXICO CITY, March 7 (Reuters) - Mexico on Friday detailed the bidding process for concessions to create two new national television networks, part of a package to boost competition in a sector dominated by Carlos Slim's phone giant America Movil and broadcaster Televisa. Bidders must seek competition clearance from new watchdog the Federal Telecommunications Institute (IFT) by June 17, in accordance with instructions that will be published by March 9 at the latest, the Federal Register said. Would-be bidders will be advised whether they can compete by Sept. 9, it added, giving details of regional frequencies up for grabs. The IFT, which was created by a reform last year aimed at boosting competition in the telecommunications sector and has the power to break up dominant players, announced the launch of the concession auction process late on Thursday. The new networks would weaken the duopoly of Mexico's two biggest players, Televisa and rival TV Azteca. Combined, which control about 95 percent of the broadcast television market. The IFT said on Thursday it had determined who is dominant, or has an oversized market share, in the telecoms and broadcast sectors, even though legislation to implement the sweeping telecoms reform of 2013 is still pending. The IFT did not name the companies in question, but said it was it was in the process of notifying the firms concerned. America Movil has about 80 percent of Mexico's fixed-line business via its Telmex unit and some 70 percent of the mobile sector through its Telcel subsidiary. A spokesman for America Movil said the company had yet to be notified. A source familiar with the ruling told Reuters broadcaster Televisa, the world's largest Spanish-language content producer, IT had been notified of its dominant position. Televisa has more than 60 percent of the TV market and has long been accused of wielding too much political power. The dominance ruling is a key part of the government's telecoms reform, which has lifted expectations that Mexico might finally tackle the extraordinary power enjoyed by a select few companies in Latin America's second largest economy. The reforms will allow the regulator to apply tougher rules to level the playing field for smaller competitors. However, a break-up of dominant companies looks unlikely in the foreseeable future.