The future of the euro may be determined in the coming weeks, as Greek voters decide whether to honor the country's international bailout and create a first test for Spain's newly built 100 billion-euro ($125 billion) banking firewall.

With Greece going to the polls in six days, the most recent surveys showed the main party opposing the terms of its bailout vying for first place. The government in Athens has “a few weeks” before exhausting its funds, making this is “a make-or-break period,” former Greek Prime Minister George Papandreou told Bloomberg Television in a June 8 interview.

The European debt crisis, now in its third year, reached a new milestone after Spain abandoned unilateral attempts to rescue its banks and became the fourth country in the 17-member currency union to seek an emergency bailout. The aid blueprint hammered out in an emergency conference call among euro finance chiefs two days ago is designed to create a line of defense if the Greek vote unleashes a new bout of market turmoil.