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Greek Prime Minister Alexis Tsipras says he has issued "a realistic proposal" to the country's international creditors in an attempt to secure a deal over its debts.

"We have submitted a realistic plan for Greece to exit the crisis," he said.

Mr Tsipras said the plan included "concessions that will be difficult".

He is due to meet European Commission President Jean-Claude Juncker in Brussels on Wednesday to discuss the Greek proposals.

Mr Tsipras' statement follows talks in Berlin late on Monday attended by the heads of both the International Monetary Fund and the European Central Bank.

International Monetary Fund chief Christine Lagarde and ECB president Mario Draghi's presence at the meeting between German Chancellor Angela Merkel and France's Francois Hollande underlined the seriousness of the talks.

Reports suggest the meeting was aimed at coming up with a "final proposal" to issue to Athens.

But Mr Tsipras, who was not included at that meeting, said he had not yet been contacted by the IMF and European officials.

"We are not waiting for them to submit a proposal, Greece is submitting a plan - it is now clear that the decision on whether they want to adjust to realism... the decision rests with the political leadership of Europe," he added.

A €300m (£216m) payment from Greece to the IMF is due on Friday.

There are fears Greece does not have the necessary funds to pay and could default on the debt, ultimately leading to its exit from the eurozone.

Friday's payment is the first of four totalling €1.5bn that Greece is due to pay to the IMF in June, and it is understood that the payments could be all bundled together and repaid in a single transaction at the end of the month.

If Greece decides to repay the funds in this way, it would have to notify the IMF, but it has not yet done so.

'Gigantic'

The country remains in a four-month long deadlock with international creditors over the release of €7.2bn in remaining bailout funds.

European lenders as well as the IMF are pushing for greater austerity reforms in return for the cash, which the Greek government has so far refused to make.

Germany's Vice-Chancellor, Sigmar Gabriel, said he supported efforts by the French and German governments to reach a deal in negotiations about Athens' massive debts, warning Greece's exit from the eurozone would have "gigantic consequences".

"The political consequences of a Greek bankruptcy in the eurozone would of course be gigantic. I think a lot of people have the impression that we're better off without Greece in the eurozone.

"The truth is that if we break the first piece out of the European house, Europe would be in a different state."

But Syriza parliamentary spokesman Nikos Filis reiterated that the government would not sign an agreement that was incompatible with its anti-austerity programme.

"If we're talking about an ultimatum... which is not within the framework of the popular mandate, it is obvious that the government cannot co-sign and accept it," Mr Filis told Antenna TV.