Grillo, who led the anti-establishment Five Star Movement to a good showing in the recent Italian elections, told Germany's Focus magazine Italy he was pessimistic about the prospects for the new government.
"Right now we are being crushed, not by the euro, but by our debt," Grillo was quoted as saying. "When the interest payments reach 100 billion euros ($130 billion) a year, we're dead."
Britain's The Daily Telegraph said Grillo predicted the center-left and center-right coalition led by Silvio Berlusconi would be history by summer and saw no reason to form an alliance with any other party since they were likely doomed.
Grillo said the best idea for Italy would be to dump the euro altogether and then re-negotiate the country's heavy international debt.
The interview with Focus hit the newsstands Saturday.