Spain paid the second-highest yield on short-term debt since the birth of the euro at an auction on Tuesday, and EU officials said Greece had little hope of meeting the terms of its bailout, casting fresh doubt on its future in the euro zone.
Though Spain has become the recent focus, Greece remains a powder keg.
If Athens were to exit the euro zone, the knock-on effects could push Spain and even Italy over the edge.
With inspectors from the EU, European Central Bank (ECB) and International Monetary Fund returning to Greece to decide whether to keep it hooked up to a €130-billion lifeline or let it go bust, EU officials said they were likely to conclude Athens cannot repay what it owes.
This time, the ECB and euro zone governments would likely have to take a hit on some of the estimated €200 billion ($240 billion) of Greek government debt they own if Athens is to be put back on a sustainable footing.