WASHINGTON — Fears of an economic slowdown are heightening anticipation of what Friday’s U.S. jobs report for January might reveal.

Stock markets have sunk after signs of weaker growth in the United States, Europe and China. Turmoil in developing countries has further spooked investors. The upheaval has renewed doubts about the Federal Reserve’s next steps.

Evidence of healthy U.S. job growth would help soothe those jitters. It would suggest that the world’s biggest economy is still expanding solidly enough to support global growth.

“The best antidote right now for all these problems is a robust U.S. economy,” said Carl Riccadonna, an economist at Deutsche Bank. “The whole world is watching, even more so than usual.”

Yet anyone looking to Friday’s report for a clear picture of the U.S. economy’s health might be disappointed. Unseasonably cold winter weather could distort January’s hiring figures. Revised estimates of job growth last year and the size of the U.S. population might further skew the data.

Another complication: A cutoff of extended unemployment benefits in December might have caused an artificial drop in January’s unemployment rate and perhaps a misleading snapshot of the job market’s health.

“Just when we need it most, the employment report may fall short,” Riccadonna said.

In the past few weeks there has been a barrage of dispiriting economic news. U.S. hiring slowed sharply in December. Employers added just 74,000 jobs, barely a third of the average gain in the previous four months. On Monday, an industry survey found that manufacturing grew much more slowly in January than in December.