Alan Greenspan can be a master of obfuscation when he wants to be. After assuming his post as chairman of the Federal Reserve Board in 1987, he said: "I've learned to mumble with great incoherence."

It's understandable: The world's most important central banker must guard his tongue, take care not to tip off markets to possible changes in monetary policy.

So when Greenspan accepted an invitation to speak at The Post's annual outlook luncheon, the editors anticipated a thoughtful speech -- but no news. It's enough, after all, for the invited businessmen and businesswomen to meet the distinguished guest -- and even get a chance to ask questions.

But what The Post audience also got last week was a carefully spelled-out, substantive message. There are preliminary signs, Greenspan said, that the U.S. economy is beginning to stabilize after a sharp drop at the end of 1990: If those signs are right, "the worst is behind us."

He added that if the Gulf crisis ends on a happy note for the United States, "it doesn't require very much imagination" to anticipate a smart rebound of business and consumer confidence. He admitted that confidence had plunged faster than he anticipated after Saddam's invasion of Kuwait.

In a nutshell, Greenspan wanted it known that things were not falling apart. And to make sure that message got across, he expanded his remarks at The Post the next day in an on-the-record interview with The Wall Street Journal, complete with a partial transcript.

"We can say with a reasonable degree of assurance," Greenspan told The Journal, "that at the moment the recession is not accelerating its pace of decline." By that time, the allied attack on Iraq had begun with initial success, resulting in a collapse of oil prices and interest rates, further brightening prospects, he felt.

Why would the normally reticent Greenspan -- who usually talks to the press through the filter of murky ground rules ranging from background to deep background to off-the-record -- be so anxious to float an optimistic pitch?

The answer from those who know him is as follows: Greenspan feels that economic forecasts current in some business circles and given wide circulation in newspapers and on TV are more negative than warranted by actual data. As this column reported previously, experts at the Brookings Institution and elsewhere also have come to believe that the anecdotal evidence conveys a feeling that the economy is in terrible shape -- but that the numbers don't support the anecdotes.

Greenspan's upbeat assessment, nonetheless, doesn't suppress all doubts. Many financial experts believe that even if the Persian Gulf war is over quickly, the American economy will still face the long-term, underlying problems that triggered a loss of consumer and business confidence in 1990. These include the weakness in the banking and thrift system, overhanging debt, a massive budget deficit and still-serious trade problems.

According to Greenspan, the most serious of these structural problems has been the credit crunch, caused because banks have been pulling back on their loans in order to improve their capital position. But Greenspan contends, "We are finally beginning to see some banks who are better capitalized beginning to pick up market share from those who are less well-capitalized. It is this process which will induce a number of banks ... to re-lend to their creditworthy customers."

In that case, the Greenspan scenario calls for a more-or-less natural recovery in consumer buying and home-building, fed by the favorable results of a short war and cheaper oil. This stimulus, from short-term factors, would more than counterbalance the "drag" from the financial sector.

One doesn't have to be too cynical to find an additional rationale for Greenspan's optimism: If he's right, then his critics at the Treasury and elsewhere will have been proved wrong. They charge that the Fed, under his direction, has moved too slowly to ease credit and thus risked deepening recession.

The Fed, according to these critics, failed to assess the true momentum of the downturn after the invasion of Kuwait, focusing too strongly on the possibilities of inflation. But Greenspan says that nothing would have been changed if the Fed had acted earlier: "I look back at the last year-and-a-half, and find few changes of significance that we would like to revisit so far as monetary policy is concerned."

No one will ever know precisely what impact an easier, more responsive Fed policy would have had. If good news from the Persian Gulf continues, Greenspan is probably right that the recession will be shortened. Yet, whether structural problems like a weak banking system can be overcome, as Greenspan seems to be betting, remains to be seen.