Greece’s finance minister issued a warning yesterday to investors betting against his cash-strapped country: “They will lose their shirts.”

George Papaconstantinou, speaking to reporters in Washington, insisted his country would be able to line up financing before debt payments come due in mid-May.

Greece is hoping to secure $40 billion from 16 European countries that also use the euro as their currency and another $13 billion from the International Monetary Fund.

Although Prime Minister George Papandreou described his country’s economy as a “sinking ship,” Papaconstantinou said speculation that Greece would default on some debt or be forced to cut or delay payments to bondholders is a “red herring.”

Even with the lifeline, investors believe this Greek drama is far from over.

“We are not buying Greek debt while so many problems remain unsolved,” Ralf Ahrens, who holds Greek bonds as part of about $20 billion he manages as head of fixed income at Frankfurt Trust, told Bloomberg News. “Asking for the package will not calm down the market.”

It remains to be seen if the country will need more aid beyond next year or whether it will be able to finance itself by then.

The tough talk ended a week in which Greece formally requested billions in emergency loans from other European countries and the IMF.