MEXICO CITY, Feb 20 (Reuters) - Mexico's National Antitrust Commission $(CAN)$ on Friday blocked Visa's planned 51% acquisition of payment processor Prosa, marking the first major assertion of authority by the country's new competition watchdog.

• The watchdog found the merger would eliminate a direct competitor, as Visa already operates its own processing services with significant market reach.

• Regulators said the deal would grant Visa access to sensitive transactional data, creating an unfair advantage over other market participants.

• Prosa is currently owned by a consortium of Mexican banks, including Banorte, HSBC, Santander, and Scotiabank.

• The decision marks the first show of strength by the CNA since Mexico's Congress scrapped the previous autonomous regulator, Cofece, in late 2024.

• Observers are now awaiting the CNA's decision on a separate proposed merger between Mexico's two leading low-cost airlines.

(Reporting by Raul Cortes and Natalia Siniawski)

((natalia.siniawski@thomsonreuters.com;))