Luxembourg's prime minister says Greece won't leave the 17-nation eurozone - arguing that an exit wouldn't be politically feasible and would carry unforeseeable risks.

Greece has been kept afloat by international loans but fallen behind on implementing reforms and austerity measures demanded in exchange, feeding speculation about a possible euro exit.

But Luxembourg's Jean-Claude Juncker, who also chairs eurozone finance ministers' meetings, was quoted Saturday as saying in an interview with Austria's Tiroler Tageszeitung newspaper: "It will not happen - unless Greece violates all the conditions and keeps to no agreements."

Juncker said he assumes Greece will redouble efforts to reach its targets - so "there is no reason to assume that this exit scenario can become relevant." He said an exit would be "technically" but not "politically" feasible.