The Nasdaq composite held up the best among the major indexes, but wavered and was up just 0.2% in recent trades. The S&P 500 also wavered and edged into positive ground after falling 0.8% Monday. Small caps outpaced the market, with the Russell 2000 index lifting 0.5% higher. The Russell ended a six-day winning streak Monday.

U.S. stocks opened little-changed on Thursday after the Nasdaq tallied a fresh record closing high on Wednesday.

"While the reciprocal tariff letters that Trump has delivered this week have largely been shrugged off by markets, Brazil’s treatment caused a shock," said William Jackson of Capital Economics.