U.S. online job postings fell slightly in November, due to a dip in demand for health care-related positions and employers' continued unease regarding economic recovery, a private research group said on Thursday.

Monster Worldwide Inc , an online careers and recruiting company, said its employment index fell to 119 points in November from 120 in October. November's reading is 17.0 percent below the 143 mark one year ago.

It was the mildest year-on-year decline in the index since September 2008.

A decrease in online job demand for the healthcare and social assistance industry put downward pressure on the index. Opportunities for healthcare practitioners and technical occupations had the largest drop, sliding 23 points in the month.

Online job availability has remained largely flat for most of 2009, according to Monster.

While job losses have continued to ease, businesses remain cautious about adding to their payrolls in light of sustained economic uncertainty, said Jesse Harriott, a vice president at Monster.

The Monster report comes ahead of the Department of Labor's weekly jobless claims data, expected to show later on Thursday that 480,000 people filed for first-time unemployment benefits, higher than the 466,000 claims filed the prior week.

On Friday the government also will release its November employment report, which is expected to show the United States shed 130,000 jobs in the month, an improvement from October figures, according to a Reuters poll of economists. The unemployment rate is forecast to remain unchanged at 10.2 percent.

Monster's index posted an increase in 10 of the 20 industries tracked, and in nine of 23 occupations in the last month.

Online job demand dipped in six of the nine U.S. census regions, with the South Atlantic region registering the largest decline.

The Monster Employment index is a monthly analysis based on a selection of corporate career sites and job boards. The margin of error is approximately plus or minus 1 percent.

(Reporting by Camille Drummond; editing by Carol Bishopric)