Activity in the U.S. services sector held at its highest level in 4-1/2 years in July, though readings for new business and employment growth weakened, a survey showed on Monday.

Financial data firm Markit said its preliminary services Purchasing Managers Index was 61.0 in July, unchanged from June and above expectations for a reading of 59.8.

A reading above 50 signals expansion in economic activity, and June's reading was the highest final reading since the survey began in October 2009.

The services sector continued to add employees, though at a slower pace. The employment index fell from 56.1, the fastest rate on record, to 52.8 in July. The new business subcomponent also fell from June's record level.

"While a cyclical upswing appears underway across the service sector, the latest survey provides some indication that a smoother ride is not yet fully entrenched," said Chris Williamson, chief economist at Markit.

"Nonetheless, service sector companies continue to perform strongly against post-recession trends, and overall the latest manufacturing and services PMI surveys suggest that the US economy has enjoyed a strong start to the second half of 2014."

Markit's final composite PMI, a weighted average of its manufacturing and services indexes, dipped to 60.9 from June's reading of 61, a level that also represented a record high for a final reading.