WASHINGTON - The American economy's steady-but-modest job growth presents political challenges for both President Barack Obama and Mitt Romney, who's closing in on the Republican presidential nomination.

Romney needs an ailing economy to fully exploit his image as an experienced business executive who can restore the U.S. economy's health, as he turned around the troubled 2002 Winter Olympics. Obama, facing re-election in November, needs job-creation momentum to persuade voters that things are moving in the right direction, even if millions of people remain unemployed.

Friday's neither-hot-nor-cold jobs report leaves both campaigns unsure of whether they can sell their narratives. Employers added 120,000 jobs last month, about half the December-February pace and well short of the 210,000 economists were expecting. Still, the unemployment rate declined from 8.3 per cent in February to 8.2 per cent, the lowest since about the time Obama took office.

Republican leaders were quick to note that the rate dropped largely because many Americans stopped looking for work and were not counted in the government survey.

The U.S. jobs picture was bleaker when Romney began his second presidential bid a year ago, emphasizing his experience in running the Olympic games and reorganizing companies while at venture capital firm Bain Capital. He said jobs grew during his four years as Massachusetts governor, but critics note that other states had more robust growth.

Republican strategists say Romney's hopes this November hang largely on his ability to convince voters that the current pace of recovery is unacceptable and he can substantially speed it up.

Romney called Friday's jobs report "weak and very troubling."

"Millions of Americans are paying a high price for President Obama's economic policies, and more and more people are growing so discouraged that they are dropping out of the labour force altogether," he said in a statement. Obama's "excuses have run out," he said.

Obama was more upbeat at a White House gathering. "Our economy has now created more than 4 million private-sector jobs over the past two years and more than 600,000 in the past three months," he said.

Democrats point to historical data showing that presidents tend to get re-elected if the economy is improving during their fourth year in office, even if it's below normal levels. In that light, the key news for Obama in Friday's report was that jobs are still being created, not that the pace was half what it was during the previous three months.

Republican strategist Brian Nick said Obama will have a hard time convincing voters they should accept a poky recovery and an unemployment rate that has exceeded 8 per cent for more than three years.

Strategists in both parties found modest comfort in Friday's report.

"To the extent there's a mixed message about some of the numbers, it gives Romney something to hold onto," said Joel Johnson, a Democrat who has worked in Congress and the Bill Clinton White House. Obama's allies must keep reminding voters that the 2008 economic collapse happened on President George W. Bush's watch and now, "we're clawing our way out," Johnson said.

Republicans say employment isn't the only important economic factor in the presidential race. High gasoline prices and concerns about federal spending and deficits also will work against Obama, they say.

Obama, meanwhile, has widened his criticisms of Romney, a tactic he may have to accelerate if employment slumps in coming months. The president said at The Associated Press annual meeting in Washington that Romney has embraced "thinly veiled social Darwinism" by backing a Republican congressional budget that would cut taxes for Americans, including the wealthiest, and reduce spending on many programs.