Washington ? Alan Greenspan, explaining one of the few economic stumbles during his long tenure at the Federal Reserve, said Friday if the Fed had tried to burst the speculative stock market bubble of the late 1990s it could have dumped the economy into a severe recession.

The man who once famously wondered whether investors were in the grip of “irrational exuberance” defended his handling of Wall Street’s long bull market during an address to a Fed-sponsored economic conference.

“The notion that a well-timed incremental tightening could have been calibrated to prevent the late 1990s bubble is almost surely an illusion,” Greenspan told participants at the economic symposium in Jackson Hole, Wyo.

Some critics have argued that the central bank made a major policy error by failing to curb stock prices as they soared into the stratosphere, setting the stage for a spectacular market crash beginning in the spring of 2000 that has seen more than $7 trillion in investor wealth wiped out.

For the Fed to have significantly influenced the level of stock prices during the market boom would have required such a big hike in interest rates that it would have run the risk of pushing the economy into a recession, Greenspan argued.

To support this view, he noted that during the long bull market that began in the early 1980s, the Fed did raise interest rates by more than 3 percentage points on two separate occasions and this only had a brief depressing effect on stock prices.

Some analysts saw Greenspan’s defense of Fed actions as a response to rare criticism of his job performance.