NEW YORK (TheStreet) -- TheStreet's Jim Cramer says the Greek situation has changed drastically in the last 48 hours and investors need to be careful. He believes the Greeks are saying to the Germans: "You have to forgive much of our debt, maybe as much as two-thirds of it, and we're going to give you nothing in return, or we're going to re-issue the drachma and you're going to get your 30% many, many years from now when we go to the Chinese and the Russians to get what we need."

Cramer says, the bottom line is, Greece has said here's our offer: Nothing.

Greece faces default, if it fails to pay back a $1.8 billion loan to the International Monetary Fund by Tuesday. If Greece does default, it could exit the eurozone. The IMF has said Greece will not get any extra time to make the repayment.

Greece's lenders are pushing for more austerity measures in exchange for continuing the bailout program. But Greek Prime Minister Alexis Tsipras has rejected those demands. Jim Cramer said in his Real Money column the Greeks want their own Marshall Plan -- an economic aid program to help the embattled country get back on its feet.

He writes, "...when you think of it like that, when you understand that the Greeks think they are deserving of a Marshall Plan while the Germans are playing this out like they are a World War I creditor to Greece, you can understand that the talks almost have to end badly."

Even if a deal is struck between Greece and its creditors, Tsipras would have to get it through parliament, and other eurozone countries would also have to ratify the new package. German Chancellor Angela Merkel has said a deal must be in place before the financial markets open on Monday. More talks will be held in the next few days but pessimism that a deal could be reached is growing.

At the time of publication, Jim Cramer's charitable trust Action Alerts PLUS held no positions in stocks mentioned.