Private employers added jobs in May at the slowest pace in nearly a decade, a new report showed, in a new alarm for the U.S. economy as President Donald Trump's intensifying trade war with China casts a pall over financial markets and the climate for business investment and hiring.  

The employers added a net 27,000 jobs during the month, the payroll firm Automatic Data Processing said Wednesday in a statement. Economists had forecast a gain of 185,000 jobs, according to FactSet. In April, the employers added 271,000 jobs. 

"Payroll growth was bound to slow in May, following April's unexpected strength, but this is a much bigger slowdown than we expected," Ian Shepherdson, chief economist at the forecasting firm Pantheon Macroeconomics, wrote Wednesday in an e-mail to clients. 

The ADP report could serve as a preview for the U.S. Labor Department's official monthly report on national employment, due out Friday.

Investors are likely to scrutinize the official report for clues about the economy's trajectory, as more Wall Street analysts and even Federal Reserve researchers warn that Trump's tariffs on China will drive up the cost of imported goods for U.S. consumers. There are also indications that some businesses are tempering expansion plans because of a lack of clarity over how the trade dispute might be resolved. 

On average, economists expect the Labor Department report, which also covers government employers, to show that nonfarm payrolls increased by 185,000 in May, based on a survey by the financial-information provider FactSet. 

But the latest reading from ADP suggests that official jobs growth in May was likely closer to 150,000, said Mark Zandi, chief economist at Moody's Analytics, who spoke to reporters Wednesday on a conference call hosted by ADP. 

And Pantheon's Shepherdson now expects the Labor Department report to show just 100,000 new positions created in May.

The private-sector job gains reported by ADP were "such a big miss" relative to expectations "that we have to temper our forecast for Friday's official number." 

Roseland, New Jersey-based ADP estimates the monthly change in private-sector employment by assessing data gleaned from its roster of payroll-processing clients, covering roughly 26 million workers in the U.S., or one out of every six. 

Some bricks-and-mortar retailers appear to have been cutting back under competition from online retailers like Amazon.com (AMZN) - Get Report  , Zandi said. 

And with U.S. unemployment currently at 3.6%, the lowest in a half century, some employers may be having trouble finding qualified workers at compensation levels they're willing to pay. 

"It's now clear that the economy's growth rate has slowed quite sharply from last year, and that is now starting to show up in the job market," Zandi told reporters on a conference call.

Zandi said he now estimates that the economy, measured in terms of gross national product, or GDP, is currently growing at an annual pace of about 1%.

That's well below the 2% second-quarter pace estimated by economists in the latest FactSet survey. It's also down from the first quarter's 3.1% clip.  

In 2018, GDP increased by 2.9%, barely missing the Trump administration's promise that his package of $1.5 trillion in tax cuts enacted in late 2017 would lead to long-term U.S. growth of 3% annually.