Growth in U.S. non-manufacturing dropped in April, while maintaining its 99-month streak of overall expansion.
The Institute of Supply Management's measure of the non-manufacturing sector sunk to 56.8 in April, two full points lower than the March reading of 58.8.
The April level fell well below expectations of 58.2, forecast by a survey of Thomson Reuters analysts.
Representatives of the 17 industries tracked in the index cited trade concerns having an impact on their business.
"The trade tensions are impacting purchasing of steel and are causing suppliers to send letters of concern regarding contracted purchases for this year and the future based on these proposed tariffs," a respondent from the construction industry said.
A representative from the finance and insurance industry said: "The international trade situation appears to be shifting on a minute-by-minute basis, which has folks nervous."
A reading above 50 indicates expansion in the service sector, and a reading below 50 signals contraction.
According to the institute's metric, the index of 17 U.S. non-manufacturing industries has seen 99 straight months of expansion.