WASHINGTON (AP) — Federal Reserve Chairman Alan Greenspan warned on Wednesday that mushrooming federal budget deficits eventually could threaten the national economy, which he said had shown “impressive gains.”

Greenspan, delivering the central bank’s twice-a-year economic report card to Congress, offered a fairly upbeat assessment and expressed hope companies would step up hiring. Hiring has been painfully slow and has become a political sore spot for President Bush.

Against that backdrop, Greenspan reaffirmed the Fed’s stance that it would be patient in considering possible increases in short-term interest rates, which now are at a 45-year low of 1 percent. The comment pleased Wall Street. The Dow Jones industrials jumped 123.85 points to close at 10,737.70 — the highest level in more than 2