Just one-fifth of the economists surveyed by the National Association for Business Economics said their companies have added to their workforces in the past three months. That is down from one-third in July. Job totals were unchanged at 69% of companies, up from 57% in July. A broad measure of job gains in the survey fell to its lowest level since October 2012.

The hiring slowdown comes as more businesses are reporting slower growth of sales and profits. Business economists also expect the economy's growth to slow in the coming year, partly because tariffs have raised prices and cut into sales for many firms.

"The U.S. economy appears to be slowing, and respondents expect still slower growth over the next 12 months," said Constance Hunter, NABE president and chief economist at the accounting firm KPMG.