The heads of the European Commission, IMF, European Central Bank and the eurozone will discuss Friday a last-ditch Greek reform plan submitted in a bid to avert financial collapse and exit from the single currency, EU sources said.

"We must speak at the highest level," one source told AFP ahead of the conference call at 1100 GMT between Jean-Claude Juncker, Christine Lagarde, Mario Draghi and Jeroen Dijsselbloem.

The four will "discuss the (Greek) proposals because we must conduct a joint analysis" at a meeting of eurozone finance ministers in Brussels on Saturday, the source added.

Greek Prime Minister Alexis Tsipras handed in the package to partners in the 19-country eurozone just two hours before a midnight deadline on Thursday.

Another EU source said the Tsipras package "creates a margin for manoeuvre to negotiate and avoid Grexit".

Eurozone officials were studying the package Friday morning. Their conclusions, as well as those made by the ECB and the IMF, will then be passed to eurozone finance ministers on Saturday.

The offer, set out in a 13-page document, concedes to Greece's paymasters several key points that Tsipras's ruling coalition -- and Greek voters -- had previously fiercely opposed.

A make-or-break summit bringing together leaders of all 28 EU nations, not just the 19 that use the euro, is due to be held on Sunday.

It will decide whether to accept Greece's reform plan in exchange for another huge bailout -- its third in five years -- amounting to tens of billions of euros, or force a "Grexit" from the eurozone.