DAVOS, Switzerland: New York University Professor Nouriel Roubini said he's never been more pessimistic about the future of European monetary union, saying Spain poses a looming threat to the euro region holding together.

"Down the line, not this year or two years from now, we could have a breakup of the monetary union," Roubini said in a Bloomberg Radio interview from the World Economic Forum's annual meeting in Davos, Switzerland. "It's a rising risk."

Roubini's concern contrasts with the view of European Central Bank President Jean-Claude Trichet who said it's "absurd" to imagine that the 16-nation euro area could splinter.