U.S. consumer confidence slipped in September to 125.1 from 134.2 in August, the Conference Board said on Tuesday. Analysts polled by Reuters had forecast the metric would come in at 133.5.
This was the biggest drop in nine months, and September's reading marks the largest shortfall relative to the economists' expectations since 2010, according to Reuters.
The board attributed the decline in part to the escalation in trade tensions between the U.S. and China.
"Consumers were less positive in their assessment of current conditions and their expectations regarding the short-term outlook also weakened," said Lynn Franco, senior director of economic indicators at the Conference Board. "While confidence could continue hovering around current levels for months to come, at some point this continued uncertainty will begin to diminish consumers' confidence in the expansion."
The confidence index for August was revised down to 134.2 from 135.1.
The Present Situation Index based on consumers' assessment of the current business and market conditions decreased from 176.0 to 169.0. The Expectations Index based on consumers' short-term outlook for income and market conditions also declined from 106.4 in August to 95.8 this month.
— Reuters contributed to this report.