SAO PAULO, Sept 18 (Reuters) - Latin American currencies and stocks were barely changed on Thursday from the previous day's close, although Brazil's Bovespa stock index slipped before the release of an opinion poll on the Oct. 5 presidential election.
The Brazilian real weakened slightly, while the Mexican peso, the Colombian peso and the Peruvian sol were all nearly flat.
Chilean markets were closed for a national holiday.
In Brazil, traders wondered how much the real would be allowed to weaken before the central bank steps up its intervention in the currency market. The real has weakened about 5 percent against the dollar over the past nine sessions, which contributes to inflation by raising the cost of imports in the local currency.
Investors have been concentrating their attention on voter polls for the election, with a new survey scheduled to be released Thursday night. They have been critical of President Dilma Rousseff for enacting policies they see as detrimental to the private sector and state-run companies.
Brazil's Bovespa stock index slipped about 0.5 percent as investors awaited the poll data. Shares of state-run oil producer Petroleo Brasileiro SA slipped about 2 percent, mostly on profit-taking after a three-day rally, traders said.
Elsewhere in Latin America, Argentina's black market peso pared Wednesday's losses, returning to the 15 per dollar level in thin trading, while the official rate stood at 8.42 per dollar.
The government on Thursday accused speculators and banks of promoting the peso's fall in an effort to destabilize President Cristina Fernandez Kirchner.
"With a quasi-fixed official (exchange) rate, devaluation expectations can only increase," wrote UBS analyst Rafael De La Fuente, citing the widening gap between the official and black market rates and the persistent loss of central bank reserves.
Argentine lawmakers approved a bill on Thursday that will allow the government to intervene in the pricing and output levels of large companies, one of a series of interventionist policies announced by Argentina since it defaulted on its debt in July. (Reporting by Asher Levine; Editing by Grant McCool)