At a conference in Jackson Hole, Wyoming, Yellen said regulations put in place after the 2007-2009 financial crisis had strengthened the financial system without impeding economic growth, and any future changes should remain modest.

"Maybe Yellen didn't comment on the economy because she's not very confident on the outlook," a New York-based portfolio manager said.

A batch of mixed US economic figures have cast a shadow on the nation's economic recovery, driving some investors to dial back bets on an interest rate increase this year.

A slower path of US rate hikes could drive up demand for high-yielding assets, benefiting currencies from emerging-market economies.

Currencies in Latin American strengthened between 0.1 percent and 1.2 percent, tracking a global decline in the US dollar.

Stock markets, however, were mixed, following a recent stretch of gains. Mexico's S&P/BVM IPC index was nearly flat, while Brazil's benchmark index slipped 0.2 percent.

Shares of meatpacker JBS SA jumped after an anti-corruption division within the Brazilian prosecutor general's office on Thursday approved a leniency deal with its controlling shareholder, J&F Investimentos SA.

Also fostering appetite for JBS shares was a Reuters report that state development bank BNDES is doing all it can to remove Chief Executive Officer Wesley Batista, who is at the center of a corruption scandal, from the company.