New York ? A closely watched gauge of future business activity fell last month for the first time since March, signaling that the pace of the nation’s economic expansion was beginning to slacken.

The Conference Board reported Monday that its Index of Leading Economic Indicators declined by 0.2 percent in September to 113.0, slightly below analysts’ expectations. The dip followed a 0.4 percent rise in August.

Analysts said the decline largely reflected the volatility of some components of the index, and that the economy was expanding, just not as rapidly.

“The story these leading indicators are telling us is this — that probably the sizzling economic growth that we experienced in the third quarter cannot continue and that it probably has already begun to downshift,” said Sung Won Sohn, chief economist with Wells Fargo & Co. in Minneapolis.

The leading indicators would have to decline for several consecutive months to merit worry that the economy was losing ground, Sohn said.

“The economy is improving … although the road ahead will likely remain bumpy,” Conference Board economist Ken Goldstein said.

The leading index measures where the overall U.S. economy is headed in the next three to six months. It stood at 100 in 1996, its base year.

Four of the 10 components of the leading index rose in September, including average weekly manufacturing hours, stock prices, orders for nondefense capital goods and manufacturers’ new orders for consumer goods. Those increases were offset by declines in other components, most noticeably a large drop in the real money supply.