The International Monetary Fund says beyond debt relief, Greece will need an extra 50 billion Euros, or 56 billion US dollars, to stabilize its current finances between this October and 2018.

The IMF also cut its forecast for Greek economic growth from 2.5% to zero.

Megan Greene, Chief Economist of Manulife Asset Management, says under the existing disputed bailout plan, Greece may need even more money to stabilize.

So, the number is bigger than most people expected. But I don't think it's big enough. It doesn't include a huge pot of money for the banks which I think Greece desperately needs for bank recapitalization."

The statement comes two days ahead of a referendum on the reforms-for-cash debt deal, with Greek Prime Minister Alexis Tsipras urging citizens to vote "No."

The European Commission, along with the IMF and the European Central Bank, wants Greece to raise taxes and slash welfare spending to meet its debt obligations.

But the Greek government argues that any new deal with Greece's creditors would have to address the country's debt by including some form of restructuring or debt relief.