WASHINGTON — Employers added only 54,000 workers in May, fewest in eight months, and the unemployment rate rose to 9.1%.

The weakening job market raises concern about an economy hampered by high gas prices and lingering effects of the Japanese tsunami and nuclear disaster.

The key question is whether the meager 54,000 jobs added last month are a temporary setback or evidence of a chronic problem.

That total is far lower than the previous three months’ average of 220,000 jobs per month.

Private companies hired only 83,000 workers in May — fewest in nearly a year.

Stocks opened fell after the report.

Local governments cut 28,000 jobs last month, the most since November. Nearly 18,000 of those jobs were in education.

Cities and counties have cut jobs for 22 straight months and have shed 446,000 jobs since September 2008.

The anemic pace of job creation presents a huge challenge to President Barack Obama’s reelection prospects next year. And it follows a string of disappointing economic data the past month that suggests the economy is hitting a soft patch after gaining some momentum.

The manufacturing sector, a key driver of the economic recovery, grew at its slowest pace in 20 months in May. Home prices are still falling and in March reached their lowest level since 2002.

Higher gasoline prices have left less money for consumers to spend on other purchases. And average wages aren’t keeping up with prices. As a result, consumer spending, which fuels about 70% of the economy, is growing sluggishly.

Economists have said that most of the factors slowing the economy are temporary. But some are now concerned that the impact is greater than they first envisioned.

“The open question is whether this is temporary and will quickly reverse itself over the next couple of months or whether this is an adjustment to a slower permanent growth rate,” said Steven Wood, chief economist for Insight Economics.

More people entered the workforce in May. But most of those new entrants couldn’t find work. That pushed the unemployment rate up from 9.0% in April. The number of unemployed rose to 13.9 million.

And the government revised the previous months’ job totals to show 39,000 fewer jobs were created in March and April than first thought.

The weakness in hiring was widespread. Manufacturers cut 5,000 jobs, first job loss in that sector in seven months. That included a drop of 3,400 jobs in the auto sector.

Car makers are cutting production because they are having trouble getting parts. Many auto parts are made in Japan, and the March 11 earthquake and tsunami in that country has disrupted supply chains.

Retailers cut 8,500 jobs, after adding 64,000 in April. And leisure and hospitality, which includes restaurants and hotels, cut 6,000 jobs. That came after they added an average of 43,000 the previous three months.

There were some bright spots in May. Professional and business services added 44,000 jobs, most in accounting, information technology services, and management.

Still, the economy needs to generate at least 100,000 jobs each month just to keep up with population growth and prevent the unemployment rate from rising. And economists say the gains need to be at least double that to drive down the unemployment rate.

About 8.5 million Americans worked part-time, even though they would have preferred full-time jobs. Another 2.2 million have stopped looking in the past year. All told, the “under-employment” rate was 15.8%, down from 15.9% the previous month.

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