SAO PAULO, Nov 5 (Reuters) - Brazilian steelmaker Companhia Siderúgica Nacional SA affirmed its original schedule for taking its mining unit public, according to a securities filing on Thursday.

Earlier on Thursday, newspaper Valor Economico reported that the company could delay plans for an initial public offering for CSN Mineração SA, citing unnamed sources.

Still, CSN said it was monitoring market conditions.

CSN Mineração SA, which owns the massive Casa de Pedra mine, is Brazil's second-largest iron ore exporter and has certified reserves of more than 3 billion tonnes, according to information on the company's website. (Reporting by Ana Mano and Carolina Mandl Editing by Alexandra Hudson and Richard Chang)