Growth in the huge US services sector slowed in March, amid uncertainty about the direction of the economy, the Institute for Supply Management said Wednesday.

The ISM non-manufacturing purchasing managers index fell to 54.4, down from 56 in February, indicating a slightly slower rate of growth in the sector that has expanded for 39 straight months.

The March slowdown was worse than analysts expected; the average estimate was a PMI reading of 55.5.

A reading above 50 indicates expansion of the sector which accounts for the bulk of US economic activity.

The dip in March activity was led by drops in prices, employment, new orders and inventories.

Fifteen of the 18 services industries surveyed reported growth in March, while three reported contraction, the association said in a statement.

"The majority of respondents' comments continue to be positive about business conditions," said Anthony Nieves, head of the ISM non-manufacturing survey committee.

"However, there is an underlying concern regarding the uncertainty of the future economy."

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