Growth in the U.S. non-manufacturing sector cooled further in July, slowing to its weakest pace in three years as trade and labor market concerns persisted, new survey data from the Institute for Supply Management showed.

The ISM's seasonally adjusted non-manufacturing index fell to 53.7% last month from 55.1% in June. A reading above 50% indicates expansion.

The consensus estimate from economists polled by Econoday was for an index reading of 55.5%.

"Respondents indicated ongoing concerns related to tariffs and employment resources. Comments remained mixed about business conditions and the overall economy," said Anthony Nieves, chair of the ISM non-manufacturing business survey committee.

The business activity or production index dropped to 53.1% from 58.2% and the new orders index went down to 54.1% from 55.8%. Indexes that measured inventories, backlog of orders and new export orders also posted declines.

Meanwhile, latest survey data from IHS Markit painted a different picture of the non-manufacturing sector. The research firm's services business activity rose to 53.0 in July from 51.5 in June amid increased new orders and improved client demand.

However, optimism among service providers weakened for the sixth straight month and fell to its lowest level since 2012, according to IHS Markit chief business economist Chris Williamson.

Williamson said companies "have grown increasingly concerned about the year ahead" due to trade and geopolitical tensions and worries over slowing economic growth.

Non-manufacturing sector growth lifted the U.S. composite PMI output index in July, IHS Markit said. The index, a weighted average of manufacturing and services business activity, registered a final reading of 52.6, up from 51.5 in June.