WASHINGTON (MarketWatch) -- The U.S. economy may be "grinding to a halt," the Conference Board said Thursday, reporting that the index of leading economic indicators fell 0.3% in February for a fifth-straight decline.

The coincident indicators -- the best overview of the current economy -- have been flat for three straight months, the private research group said. Read the full report.

"Growth will be weak this spring," said Ken Goldstein, labor economist for the Conference Board. "A small contraction in economic activity cannot be ruled out."

The leading indicators are designed to forecast economic activity six to nine months ahead. The last time the leading index fell for five straight months was in early 2001, at the beginning of the last recession.

The index "has sunk to levels that are generally seen only during recessions or the period immediately preceding one," wrote Tim Quinlan, an economist for Wachovia.

The coincident indicators are the same four indicators used by the business-cycle dating committee of the National Bureau of Economic Research to judge whether the economy is in a recession or is expanding. See the latest story on the recession indicators.

Five of the 10 leading indicators fell in February: jobless claims, building permits, delivery times, consumer expectations, and stock prices. Four indicators rose: Real money supply, interest rate spreads, orders for capital goods and orders for consumer goods. The factory workweek was unchanged.

The Fed's massive stimulus efforts boosted money supply and the yield curve, Quinlan noted. "Help is on the way."

Several of the indicators -- such as real money supply and the orders data -- are estimated because they have not yet been officially reported. The January leading index was revised lower to a 0.4% decline from a 0.1% decline.

In a separate report Thursday, the Labor Department said initial jobless claims -- one of the 10 leading indicators -- rose to 378,000 last week, a sign of a weaker labor market. See full story.

In another report, the Philadelphia Federal Reserve Bank said sentiment among manufacturing firms in its region improved in March but remained at a very low level. The Philly Fed index improved to negative 17.4 from negative 24. Negative readings show that more firms think business conditions are bad than think they are good. See full story.

Over the past six months, the leading index was down 1.5%, a slight improvement from the 2.3% decline from July through January. Just two of the 10 indicators are up in the past six months.

The coincident index was flat over the past six months, with two of the four coincident indicators rising.

The lagging index rose 0.2% in February and is up 1.7% in the past six months.