ESM's Regling warns of Greek banking system collapse without 3rd bailout

German Finance Minister Wolfgang Schaeuble attends the weekly cabinet meeting at the Chancellery in Berlin, Germany, July 15, 2015. REUTERS/Axel Schmidt

BERLIN (Reuters) - The head of the European Stability Mechanism on Thursday warned of a collapse in the Greek banking system if the country does not secure a third bailout, saying this would have consequences for the entire euro zone.

"If everything should fail, then the Greek banking system will collapse," Klaus Regling, head of the European Stability Mechanism (ESM), told German broadcaster ARD, adding that the four biggest Greek banks were systemically relevant.