On Thursday, leftist Chilean presidential candidate Alejandro Guillier - who is competing in a tight runoff after coming in second in first-round elections on Sunday - said he was open to eliminating Chile's quasi-private pension fund system in favor of a state-run model.
Additionally, workers at BHP Billiton Ltd's Escondida copper mine in Chile, the world's biggest, walked off the job temporarily, spooking investors in the mining-dependent country. The IPSA was off 1.27 percent in midafternoon trading.
Brazil's Bovespa was down 0.72 percent as President Michel Temer continues to face difficulties pushing through a pension reform seen as key to shoring up the nation's fiscal health.
On Wednesday night, the congressman in charge of drafting the reform presented a new version in an event at Temer's official residence. However, attendance was poorer that expected, which some analysts interpreted as a sign of relatively weak support for the measure.
Among the poorly performing major constituents of the index was steelmaker Usinas Siderurgicas de Minas Gerais SA , which was off 1.2 percent.