Debt Crisis May Spread to US, Japan: Roub

Despite Thursday's unexplained surge in selling that drove the Dow down 900 points, the stock markets are being driven lower by fears over the global economy and the debt crisis spreading, economist Nouriel Roubini, of RGE Monitor, told CNBC Friday.

Photo: Oliver Quillia for CNBC Nouriel Roubini

Greece is just the "tip of the iceberg" for the problem of accumulating debt, and it must be solved by raising taxes and cutting spending, if not default will follow, Roubini said.

"My concern is eventually, not this year, it may spread to Japan and in the US," he said.

"In my view there's going to be a restructuring of the debt in Greece," Roubini added.

Euro zone members who borrow in their own currency actually act more like emerging-market countries who borrow in other currencies, because they don't have control over monetary policy, he said. Read more