If you thought the U.S. was out of the woods from the so-called Great Recession, think again, says Yale economics professor Robert Shiller.

Shiller, who teaches the perennially popular course “Financial Markets” in the spring, was featured in the Wall Street Journal’s video series “The Big Interview” on Friday saying the United States may be entering into the second phase of the recession, a so-called “double dip.”

“It’s something I’ve been warning about for some time,” Shiller told the Journal’s Simon Constable in the 20-minute interview, adding that the phenomenon is a rarity.

Shiller goes on to explain that the Federal Reserve is “out of ammunition” to prop up a nation facing low morale due to high unemployment rates and falling housing prices, among other economic factors.

The professor’s comments come on the heels of Fed chairman Ben Bernanke’s announcement that the central bank is willing and prepared to take “unconventional measures” to bolster growth.