WASHINGTON — U.S. employers dramatically stepped up hiring in December, adding 312,000 jobs in an encouraging display of strength for an economy in the midst of a trade war, slowing global growth and a partial government shutdown.

The Labor Department said Friday that the unemployment rate rose slightly to 3.9 percent, but that reflected a surge in job seekers — a positive for growth.

Average hourly pay improved 3.2 percent from a year ago, up from 2.7 percent at the end of 2017.

The jolt in hiring offered a dose of reassurance after a tumultuous few months on the financial markets.

Stocks surged on the news, along with word that the U.S. and China will hold trade talks next week and comments from Federal Reserve Chairman Jerome Powell that the U.S. central bank will be flexible in judging whether to raise interest rates.

The Dow Jones industrial average climbed roughly 700 points in early afternoon trading, an increase of about 3 percent.

Job growth at this pace is a sign that the economy will continue to expand for a 10th straight year, even if overall growth slows somewhat because of the waning stimulus from President Donald Trump’s tax cuts.

“The labor market is very strong even though the economy appears to be slowing,” said Eric Winograd, senior U.S. economist at the investment management firm AllianceBernstein. “Those two things cannot coexist for very long. Either weakening demand will lead firms to dial back the pace of hiring or the robust pace of hiring will lead firms to ramp back up production.”

In recent weeks, financial markets have been increasingly worried about the path of economic growth this year. The Dow suffered its worst December decline since the middle of the Depression in 1931 as surveys of economists and business leaders suggested the United States could be in a recession by 2020.

The expected continuation of steady job growth suggests that some of the risks might be — for the moment, anyway — overblown. However, the stock market will have to weigh whether the strong job growth will lead the Fed to raises rates even more than anticipated.

Trump called the job growth “GREAT” on Twitter. But Kevin Hassett, chairman of the White House Council of Economic Advisers, told reporters on Thursday that the next jobs report for January could be weak if the government shutdown continues. Hundreds of thousands of government employees put out of work would lower the job totals.

“So when we see the January jobs number, it could be a big negative,” Hassett said.

The health care, food services, construction and manufacturing sectors were the primary contributors to last month’s hiring.