JPMorgan Chase & Co Chief Executive Jamie Dimon believes a Greek exit from the euro could have “catastrophic” consequences for other countries and the single currency.

If Greece had defaulted when its debt problems became clear, it «wouldn't have been a big deal,» Dimon said during a talk at Rice University, according to the Wall Street Journal. But a Greek exit from the euro would have been «catastrophic,» as it would have triggered a run on Italy and Spain, according to Dimon.

The Wall Street Journal reports Dimon as saying this would also have sown confusion among investors and businesses trying to assess whether contracts would be priced in euros or in local currencies.

"When they restructure the euro treaty, they should allow an orderly exit,» the JPMorgan CEO said.