The man made famous by his bets against subprime mortgages, billionaire Jeff Greene, remains pessimistic about American consumers and the outlook for commercial real estate.

"I'm very pessimistic about the economy," Greene said in an interview with CNBC's "Squawk Box." "...We're in a difficult time."

Oliver Quillia for cnbc.com

According to Greene, commercial real estate deals have yet to reach truly distressed levels.

"There is a still a huge disconnect between what sellers are asking for properties and what buyers are willing to pay. There are no deals yet," he said, adding that it is likely that by the time deals come along, everyone will be "so beat up they won't want to buy."

As for real estate investment trusts, he thinks they are a "slow-speed train wreck."

Greene expects REITs will be hit by a "triple-whammy" that includes tenants renewing leases at highly reduced rents, higher financing costs and equity dilution.

The backdrop for Greene's outlook is the opinion that the U.S. could suffer through a five-to-seven year period of slow growth.

"We just had this huge, huge ten-year party," Greene said. "I think that basically what Americans did was not live off their income; they lived off their assets...now we're cleaning up this mess, and I think the consumer is shell-shocked."

Greene expects it will be a long time before Americans are willing to jump back in and get leveraged again.

According to investor Philip Blumberg, who appeared on CNBC with Greene, the real troubles for the commercial real estate market have yet to materialize.

• Video: Greene on Why GDP Will Decline 3%-6% This Year

Blumberg, who is the CEO of Blumberg Capital Partners, said the real story is the outstanding debt in this market.

"Think about this: In the next three years, 2010 — that's when it really starts — to 2013, we've got about $300 billion in (commercial mortgage-backed securities), of which $70 to $100 billion is not refinanceable. But to put it in real perspective, on top of this is $1 trillion in bank loans written in the same timeframe, with the same dubious underwriting, coming due in that period."

Blumberg expects this wave of debt will be a "real blow to the belly of the banking sector."

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