(Bloomberg News) Companies in the U.S. added fewer workers than forecast in May, a sign that job growth is struggling to gain momentum, data from a private report based on payrolls showed today.

Employment increased by 38,000 last month, the smallest increase since September, from a revised 177,000 in April, according to figures from ADP Employer Services. The median estimate in the Bloomberg News survey called for a 175,000 advance for May.

Such gains in employment are insufficient to help the world's largest economy accelerate after a surge in food and fuel costs earlier this year. Businesses added 207,000 jobs last month after a 268,000 gain in April and the jobless rate dipped to 8.9 percent from 9 percent, economists project a Labor Department report to show in two days.

"Although labor conditions remain weak we anticipate further improvement taking hold in the coming months as conditions gradually improve," Maxwell Clarke, chief U.S. economist at IDEAglobal in New York, said before the report. " As conditions improve, we expect to see some further downward pressure in the unemployment rate."

Estimates for the ADP data ranged from increases of 125,000 to 200,000, according to the Bloomberg survey of 37 economists.

Gauging Accuracy

Over the previous six reports, ADP's initial figure was closest to the Labor Department's first estimate of private payrolls in February, when it understated the gain in jobs by 5,000. The estimate was least accurate in December, when it overestimated the increase in employment by 184,000.

Another report today showed employers announced fewer job cuts in May than a year earlier, signaling the labor market is improving. Planned firings dropped 4.3 percent to 37,135 last month from May 2010, according to figures from Chicago-based Challenger, Gray & Christmas Inc. Government and nonprofit agencies had the most cutbacks.

Today's ADP report showed a decrease of 10,000 workers in goods-producing industries, which includes manufacturers and construction companies. Employment at factories fell by 9,000.

Service providers added 48,000 workers, ADP said.

Companies employing more than 499 workers cut their workforces by 19,000 jobs. Medium-sized businesses, with 50 to 499 employees, created 30,000 jobs and small companies increased payrolls by 27,000, ADP said.

Japan Disaster

The drop in manufacturing may reflect supply disruptions caused by the earthquake and tsunami in Japan, Joel Prakken, chairman of Macroeconomic Advisers LLC in St. Louis, which produces the data with ADP, said in an interview on CNBC Television.

Some companies are already looking beyond the temporary slowdown and are making plans to expand payrolls further in 2012. General Motors Co. said last week it will invest $69 million and add 2,500 jobs to start making new models at the Detroit plant that builds the Chevrolet Volt plug-in hybrid as the automaker boosts U.S. production.

Overall payrolls, which include government workers, probably rose by 180,000 in May after climbing by 244,000 a month earlier, according to the median forecast of economists surveyed before the Labor Department's June 3 report.

Federal Reserve officials have said the jobless rate "remains elevated" at 9 percent, one reason central bankers pledged at their last meeting to complete an asset-purchase plan by the end of this month and to keep borrowing costs near zero.

The ADP report is based on data from about 340,000 businesses employing more than 21 million workers.