WASHINGTON (AP) _ While calling the economy's current performance ``outstanding,'' Federal Reserve Chairman Alan Greenspan expressed worries today that the high-flying stock market could be headed for a tumble that could spell serious trouble down the road.

Greenspan, in testimony before the House Ways and Means Committee, said nothing to directly indicate whether the Fed would be changing interest rates any time soon.

But his expressions of concern about the altitude of the stock market gave support to views that the central bank is not likely to rush to cut rates further unless global turmoil sends markets into a severe downturn such as occurred last fall.

Greenspan's remarks today were his most extensive worrying aloud about whether prices had risen too high since his famous comments about ``irrational exuberance'' in December 1996, when the Dow Jones industrial average was nearly 3,000 points lower than it is today.

Greenspan noted that stocks have been climbing into record territory this year and called this fact unusual, given that corporate profits, the underpinning of stock prices, have been weaker.

He said this weakness in profits raised the ``possibility that the recent performance of the equity markets will have difficulty in being sustained. The level of equity prices would appear to envision substantially greater growth of profits than has been experienced of late.''

Greenspan said a tumble in stock prices could quickly spillover into the real economy through what economists call the ``wealth effect,'' the fact that consumers spend more when their net worth is rising and cut back when they face reversals.

It has been robust consumer spending that in large part has kept the U.S. economy steaming ahead in the face of the severe global turmoil that began in Asia in mid-1977.

``A decline in equity (stock) values, especially a severe one, could lead to a considerable weakening of consumer demand,'' Greenspan said.