With stock indexes reaching new highs on an almost daily basis, economist Nouriel Roubini says equities may be moving toward a crash.

While stocks aren’t in bubble territory yet, a "huge rally in risk assets" during the next two years puts markets in danger of a big crash, Roubini said at a private dinner in Las Vegas, according to CNBC.

There is a "huge gap between sentiment on Wall Street and Main Street" and the real U.S. economy remains weak, the New York University economics professor explained.

Video: Economist Predicts 'Unthinkable' for 2013

The Standard & Poor's 500 Index marked its fourth consecutive record close Tuesday and the Dow Jones Industrial Average closed above 15,000 for the first time. U.S. stocks are in the fifth year of a bull market amid three rounds of bond purchases by the Federal Reserve, according to Bloomberg.

Roubini added that yields will "normalize very slowly."

The Fed is buying $85 billion of Treasurys and mortgage-backed securities each month to support the economy by putting downward pressure on borrowing costs.

Once the Fed and other central banks stop their quantitative easing programs, a financial crisis much worse than the one seen in 2008 will be triggered, said David Roche, president of Independent Strategy.

When the easy money policies end, sovereign bond yields, including U.S. Treasurys, German bunds and U.K. gilts, will spike significantly, prompting a crash.

"As long as the central bankers print money, the only way to have to distribute it is [for governments] to buy 70 percent of new bond issuance in these safe-haven bond markets," he told CNBC.

"As long as they go on doing that, the yields won't go up, and the day they stop, the yields will go up by so much we will have a financial crisis on our hands," Roche added.

"You are looking at a massive capital loss on a mark-to-market basis for a lot of financial institutions in the world and for people who have put their savings into those bonds, which will hit demand and hit the real economy, because if wealth goes down people's optimism about the world economy will fade."

Video: Economist Predicts 'Unthinkable' for 2013