MILAN, Oct 15 (Reuters) - Italy's third-largest bank Banco BPM has signed a non-disclosure agreement (NDA) to explore a potential tie-up with Credit Agricole Italy as part of ongoing discussions with the French group, a source familiar with the matter said.

The source said the agreement had been signed as a customary step that allows the exchange of confidential information and did not prevent Banco BPM from discussing other merger options.

Banco BPM and Credit Agricole have been in talks over the future of their Agos consumer credit joint-venture, but sources with knowledge of the matter had told Reuters there had also been preliminary contacts over a possible deal.

Il Messaggero daily reported on Thursday the two banks were preparing to enter formal merger talks.

A person close to Banco BPM said earlier on Thursday recent contacts with Credit Agricole had still centred on Agos, though Banco BPM was open to discussing merger options with all potential partners. Credit Agricole declined to comment. (Reporting by Andrea Mandala, editing by Valentina Za)