U.S. private employers unexpectedly shed jobs in September, reinforcing the belief that the U.S. Federal Reserve will embark on another round of monetary policy stimulus to support the economic recovery as early as next month.

ADP's national employment report on Wednesday said U.S. private employer payrolls fell by 39,000 jobs in September. By contrast a Reuters consensus forecast was for an increase of 24,000 jobs.

It's not earth-shatteringly bad, but it's worse than expected, said Zach Pandl, U.S. economist at Nomura Securities in New York.

Over the past six months the ADP number has underperformed nonfarm payrolls by 80,000, Pandl said.

The Federal Reserve's decision, due at their early November policy meeting, will likely hinge on inflation and labor market developments, and the monthly U.S. Labor Department report on employment on Friday.

U.S. nonfarm payrolls on Friday will likely show an unchanged reading in September as a further unwinding of temporary Census jobs and layoffs at state and local governments offset a slight pickup in private hiring, according to a Reuters survey.

It's still possible to get a strong positive payrolls number, but it does suggest some downside risk and it trims the upper tail off of the potential outcomes for Friday, Pandl said. But in general if we get anything looking like this on Friday, 'QE2' is a done deal at the November 3 (Fed) meeting.

U.S. stocks were slightly higher on opening after the data with the S&P 500 stock index .SPX up 0.8 percent. U.S. Treasury debt gained in price, while the U.S. dollar hit a 15-year low versus the yen.

Another report on Wednesday showed the number of planned layoffs at U.S. firms rose slightly in September, though it was the second lowest level of the year, according to the report from global outplacement consultancy Challenger, Gray & Christmas, Inc.

This does not bode particularly well for private sector employment in Friday's employment situation report although some of the largest divergences between the ADP employment report and the employment situation report have been in the last couple of months, said Steven Wood, chief economist at Insight Economics in Danville, California.

The Federal Reserve -- the U.S. central bank -- last month said it was ready to inject more money into the economy if needed to shore up a sluggish recovery from the worst downturn since the 1930s and prevent a damaging bout of deflation.

The Fed, which has already injected $1.7 trillion into the economy by purchasing mortgage-related and government bonds, next meets on November 2-3.

IMF CUTS FORECAST FOR U.S. ECONOMIC GROWTH

Meanwhile, the International Monetary Fund said on Wednesday U.S. economic growth will be much weaker this year and in 2011 than previously thought, dimming hopes for bringing down unemployment any time soon.

In a sober assessment of the U.S. outlook, the IMF cut its estimate for 2010 growth to 2.6 percent from the 3.3 percent it forecast in July and said gross domestic product will expand 2.3 percent in 2011 instead of 2.9 percent.

One bright spot emerged on Wednesday that offered a glimmer of hope for the hard-hit U.S. housing market.

The Mortgage Bankers Association said U.S. mortgage applications for home purchasing rose for a second straight week, with demand at its highest level since early May as potential homeowners took advantage of record low interest rates.

The housing market, however, remains highly vulnerable to setbacks and most economists believe a recovery will be elusive until the labor market improves.

(Additional Reporting by Emily Flitter in New York and Glenn Somerville in Washington)

California Unemployment Inflation