U.S. service firms grew more quickly last month as production, hiring and new orders increased, a sign that the economy is accelerating after dipping at the start of the year.

The Institute for Supply Management says its service-sector index rose to 56.3 in May from 55.2 in April. Any reading above 50 indicates expansion. The report points to solid growth after a brutal winter caused the economy to shrink 1% during the January-March quarter.

According to ISM, 17 non-manufacturing industries reported growth in May and only one (mining) reported contraction. "The majority of respondents' comments indicate that that there is steady incremental growth and project a positive outlook on business conditions," said the report.

The government issues its May jobs report on Friday. Employers added 288,000 jobs in April, and the unemployment rate fell to 6.3%. Economists expect 220,000 jobs were created in May, according to a FactSet survey.

But payroll processer ADP said Wednesday that private employers pulled back on hiring in May, adding just 179,000 jobs.