Corporate America continued to hire workers in September, albeit at a more tempered pace, according to payroll firm Automatic Data Processing in a sign the U.S. economy may be starting to feel the impact of slowing growth elsewhere around the world. 

Private employers added 135,000 jobs during the month, ADP said, below economists' average forecast of a gain of 142,500 and also below the revised 157,000 private jobs tallied up by ADP in August.

The ADP private-sector report is a precursor to the official U.S. jobs report that will be released Friday. Economists are currently projecting that the Bureau of Labor Statistics report will reveal that 145,000 new jobs were created in September, up from August's 130,000 gain, based on a survey by data provider FactSet. The unemployment rate is seen holding steady at 3.7%, with average hourly earnings "continuing to show heat" with a monthly increase of 0.3%.

The ADP report confirmed that U.S. private companies took a more moderate approach to hiring last month amid ongoing uncertainty surrounding President Donald Trump's trade war with China as well as growing signs of more-tempered U.S. growth at the hands of a still-ongoing global manufacturing recession.

It also pointed to what market-watchers have been waiting for: signs that American companies are starting to feel the pinch from U.S. consumers, who have so far countered the negative impact of slowing global growth. 

"The job market has shown signs of a slowdown," said Ahu Yildirmaz, vice president and co-head of the ADP Research Institute. "The average monthly job growth for the past three months is 145,000, down from 214,000 for the same time period last year."

#ADP employment change +135K, slightly below expectations.

— jeroen blokland (@jsblokland) October 2, 2019

Small- and medium-sized companies did roughly the same amount of hiring as big firms that month, with companies in the 20-49 employees range adding 25,000 jobs, and companies with between 50 and 499 workers adding 39,000 new jobs. Large business with more than 1,000 workers hired 52,000 new positions last month, ADP said.

By sector, services accounted for the bulk of new jobs last month, with education and health services-focused firms adding on 42,000 new workers, followed by "trade/transportation/utilities" with 28,000, "professional/business services" with 20,000, and "leisure/hospitality" with 18,000.

On the flip side, goods-producing industries like construction and manufacturing added a more modest 9,000 and 2,000 jobs, respectively, last month, while natural the resources and mining sector shed some 3,000 positions, ADP said. 

"Businesses have turned more cautious in their hiring," said Moody's Chief Economist Mark Zandi."Small businesses have become especially hesitant. If businesses pull back any further, unemployment will begin to rise."

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