In May, businesses in the U.S. added new jobs at a pace that was slower than expected, according to a private hiring survey published on Wednesday.

Only 179,000 new jobs were added to the economy -- the fewest jobs in four months -- although economists originally estimated that there were 210,000 job gains last month, according to the national employment report compiled by payroll processor Automatic Data Processing, Inc. (ADP) and forecasting firm Moody's Analytics.

In the previous month, 215,000 private-sector jobs were created. Experts say that the new report could signal that the labor market slowed down after achieving strong gains earlier this year.

"Job growth moderated in May. The slowing in growth was concentrated in Professional/Business Services and companies with 50-999 employees," said Mark Zandi, chief economist at Moody's Analytics that compiles the data, reports The Wall Street Journal. "The job market has yet to break out from the pace of growth that has prevailed over the last three years."

Last month, small businesses added 82,000 jobs, while mid-size companies added 61,000 and large companies added 37,000, reports USA Today.

Data from the ADP could also be used as an indication that the Labor Department's employment survey, to be released Friday, may also show a modest slowdown from April's huge gain of 288,000 jobs, reports the Associated Press. Both of the reports show that average job gains topped 200,000 from February to March.  However, the ADP only surveys private businesses and tend to differ from the government's report, which is more comprehensive.

Economists predict that the government's figures will show that employers added 220,000 jobs in May, according to a FactSet survey.

"The labor market remains strong and the economy is still recovering from the weather-induced hit in the first quarter," said Paul Dales, senior U.S. economist at Capital Economics, in a note to clients.