U.S. private-sector employment rose by 170,000 in January, seasonally adjusted, according to the national employment report released today by Automatic Data Processing Inc. (NASD: ADP). Meanwhile, December’s employment growth was revised downward to 292,000, from the initially reported 325,000.

The service-providing sector added 152,000 jobs, while employment in the goods-producing sector rose by 18,000 in January.

“Over the last three months, the monthly gains in employment shown in the ADP national employment report have averaged 223,000, compared to 163,000 per month over all of 2011,” said ADP President and CEO Carlos Rodriguez. “This is a positive development that we hope will continue throughout the course of 2012.”

Small businesses, those with fewer than 50 workers, added 95,000 jobs in January. Large business, those with 500 or more workers, gained 3,000 jobs, while midsize businesses added 72,000 jobs.

The report is derived from a sample of ADP data that averaged approximately 344,000 U.S. business clients in 2011 representing more than 21 million U.S. employees.