MEXICO CITY, Aug 18 (Reuters) - Fitch Ratings on Thursday said it has downgraded Mexican leasing firm Unifin Financiera's long-and short-term foreign and local currency issuer default ratings (IDRs) to 'RD' from 'C', following the firm's payment default on some credit facilities.

Fitch said it would reevaluate Unifin's financial flexibility if the company undergoes a formal debt restructuring process. (Reporting by Carolina Pulice; Writing by Kylie Madry; Editing by Anthony Esposito)