* Brazil Bovespa down 0.34 pct, Mexico IPC falls 0.33 pct
MEXICO CITY, Jan 21 (Reuters) - Brazilian stocks fell to a five-month low on Tuesday, led by shares of steelmaker CSN, on concerns the company could be forced to disburse up to $3 billion to buy out partners in its Namisa iron ore unit.
Mexico's IPC index fell for the third session in four, while Chile's bourse edged lower.
After initial gains of as much as 0.8 percent, Brazil's benchmark Bovespa stock index was down 0.34 percent by close, hitting its lowest level in over five months.
Shares of CSN, or Companhia Siderurgica Nacional SA , plunged 7.46 percent, their biggest one-day drop since Sept. 2012, pushing the index into negative territory.
Local newswire Agencia Estado, citing unidentified sources with knowledge of the situation, reported that an agreement between CSN and a group of Asian trading companies and steel mills over Namisa's ownership was taking longer than expected.
Investors are worried CSN, which has been struggling with weak trends in its steel and iron ore units and rising debt, would have to compensate partners for problems with Namisa. Itochu Corp and other partners could exercise an option to sell their stake to CSN worth as much as $3 billion.
CSN did not respond to a request for comment.
* Itaú Unibanco Holding SA, Brazil's largest non-government bank, rose 1.41 percent, helping support the index, while rival Banco Bradesco SA advanced 1.15 percent.
* Consumer delinquencies in Brazil fell in 2013 for the first time in 14 years, research firm Serasa Experian said on Tuesday. The numbers could at first glance spell a brighter outlook for private-sector lenders, which have seen quarterly profit recover recently thanks to prudent credit disbursement policies.
* Shares of state-run oil company Petroleo Brasileiro SA , known as Petrobras, advanced for the first session in four, rising 1.05 percent.
* Mexico's IPC index lost 0.33 percent to 41,838.63.
* Mining firm Grupo Mexico lost 2.45 percent, contributing most to the index's losses, while cement manufacturer Cemex advanced 2.47 percent.
* Chile's IPSA index gave up slight morning gains, returning to negative territory for a second straight session.
* Retailer Falabella slipped 0.81 percent, while Banco de Chile advanced 0.78 percent.