U.S. employers added 18,000 workers in June, the fewest in nine months, and the unemployment rate unexpectedly climbed, indicating a struggling labor market.

The increase in payrolls followed a 25,000 gain that was less than half the rise initially estimated, Labor Department data showed today in Washington. The median estimate in a Bloomberg News survey called for a June gain of 105,000. The unemployment rate rose to 9.2 percent, the highest level this year. Hiring by companies, which excludes government agencies, was the weakest since May 2010.

Stock-index futures plunged and Treasuries rose as the absence of stronger job growth caused earnings to stagnate, posing a threat to consumer spending that accounts for 70 percent of the economy. The second-quarter slowdown in hiring underscores a recovery that Federal Reserve Chairman Ben S. Bernanke said is "frustratingly slow."