Reducing U.S. long-term deficits will inevitably cause economic pain, former Federal Reserve Chairman Alan Greenspan said Thursday.

“The presumption that we’re going to have a painless solution to this, I think, is fantasy,” Greenspan said in a Bloomberg TV interview. “There are a lot of risks out there but the one thing I can be reasonably certain of is we won’t get through this whole issue without some pain.”

The U.S. faces twin fiscal challenges with more than $600 billion of spending cuts and tax increases scheduled to hit at the beginning of next year, threatening to send the economy into an austerity-induced recession, even as rising long-run deficits may prove unsustainable.

Greenspan, 86, who preceded Ben S. Bernanke as chairman of the central bank, blamed U.S. deficits on growth in spending and blamed both political parties, saying “strangely enough, and ironically, the spending surge which is creating the problem here is fundamentally both Republicans and Democrats.”

While Bernanke has refrained from identifying the mix of fiscal changes that are needed to stabilize fiscal policy, Greenspan said the “key part” of the deficit is “government social benefits to persons.”

Greenspan said the economy is poised for 2 percent growth, without specifying a time frame.