Greece will have to leave the eurozone if it fails to reach a deal on a second, 130 billion euro bailout with its international lenders.
That unusually stark warning from government spokesman Pantelis Kapsis seemed to be aimed at building support among the Greeks for tough austerity measures.
Kapsis told Skai TV: “The bailout agreement needs to be signed otherwise we will be out of the markets, out of the euro. The situation will be much worse.”
EU, International Monetary Fund and European Central Bank inspectors have to agree details of the rescue plan this month.
Athens risks a default if there is no deal before a major bond redemption due in March.
Greece and its EU partners have repeatedly ruled out a euro exit, which could drag the single currency bloc even deeper into crisis, and usually avoid saying this is a possible scenario.
But top Greek officials, who need to push through unpopular reforms to clinch the bailout deal, have warned over the past few days that a return to the drachma would be “hell” and that the country must stick to austerity to avoid it.
Opinion polls show Greek voters want the government to do all it takes to stay in the euro even if they disagree with austerity reforms.