Greece has missed a $1.8 billion payment to the International Monetary Fund as it stands on the brink of a financial meltdown. The deadline coincided with the end of Greece’s international bailout, leaving it without an infusion of the money it needs to meet its obligations. On Tuesday, European creditors rejected a last-minute proposal from Greek Prime Minister Alexis Tsipras for a new financial lifeline. Jeroen Dijsselbloem, the head of the Eurogroup of finance ministers, said a new bailout program could be negotiated, but only if the Greek government backs down from its rejection of austerity demands.

Jeroen Dijsselbloem: “What can change is the political stance of the Greek government that has led to this unfortunate situation. And what we could consider, but we will have another conference call tomorrow, is further talks on a new program. But given the current political position that the Greek government is taking, it’s very difficult to have constructive talks.”

The Financial Times is reporting Tsipras has made new concessions in a bid to complete an agreement. Greece is set to hold a referendum on Sunday on whether to accept an austerity package of budget cuts and tax hikes in exchange for new loans. On Tuesday, tens of thousands of people rallied in Athens in support of a “yes” vote, one day after a similarly sized crowd rallied against the austerity demands. With its missed payment, Greece becomes the first developed nation to fall into arrears with the IMF, and also for the largest-ever amount.