Twelve of Greece’s biggest creditors announced Monday they are backing a deal to give it relief from its debt burden, as questions remained whether enough lenders would get behind the deal by Thursday’s deadline.

The statement by the dozen banks, insurers and investment funds came amid concern that not enough investors will voluntarily swap their Greek government bonds for new ones with a much lower face value, longer repayment deadlines and lower interest rates.

Acceptance would be a significant milestone in resolving the two-year-old Greek debt crisis, but the worry is that some creditors will not sign up.

Some bondholders, such as hedge funds, also bought contracts that in effect serve as insurance against a default and stand to benefit from those if the country goes broke,

Without the debt relief, Greece won't get a second, €130 billion ($170 billion Canadian) bailout from the other euro countries and the International Monetary Fund.

Greece has threatened to withdraw the deal — a move that would automatically lead to an uncontrolled default — if not enough lenders agree to it.

The announcement came Greece’s finance minister revealed that bank deposits in Greece have fallen by €70 billion ($91.7 billion) since the start of the crisis in 2009, an indication of the massive loss of confidence in the economy as it repeatedly came close to bankruptcy.

Evangelos Venizelos said much of the withdrawals were spent as families and businesses eat into their savings, or hoarded by households preparing for a default or Greece's exit from the euro.

Bondholders will lose 75%

"This money, if it existed in the banks, would allow for loans to be made to businesses, for the economy to move, for unemployment to be tackled," Venizelos said in an interview on Antenna Television.

The terms of the private debt relief agreement, which would leave investors with losses of as much as 75 per cent, could cut Greece's €350 billion ($459 billion) debt by as much as €107 billion ($140.2 billion).

Without the bailout, they could likely face much bigger losses, not only on their Greek holdings but also on investments in other vulnerable euro countries, whose value could tumble in any ensuing turmoil in financial markets.

The 12 backing the deal include German insurer Allianz, French bank BNP Paribas, Germany's Commerzbank and Deutsche Bank, as well as Greece's Eurobank EFG and National Bank of Greece.

Their participation doesn't come as a surprise, as they were involved in negotiating the deal.

Many of them also have close links to eurozone governments, which will be funding the bailout.

Greek politicians have said that they want investors holding 90 per cent of the debt in private hands to sign up to the deal, but that a participation rate of at least 75 per cent may be acceptable.

In addition, the parliament in Athens has passed legislation that could allow a majority of 66 per cent of investors to force the deal on potential holdouts.

That, however, could trigger payouts by banks that have sold credit default swaps — complex financial products that act as bond insurance — which the eurozone fears could cause panic on financial markets.

With files from The Associated Press