The International Monetary Fund is estimating it needs to raise up to $600 billion in new resources to lend to countries struggling with the fallout from the growing euro zone debt crisis, IMF sources said today.

The news comes as international creditors and the Greek government prepare to resume talks that broke down last week over the interest rate Greece will offer on new bonds and a plan to enforce private investor losses.

It also comes after revised growth forecasts from the German Government and the World Bank.

While the IMF estimates it will need $500 billlion of the money to lend to member countries, the remaining $100 billion will be used as a "protection buffer," the sources, who were present at an IMF board discussion on the issue yesterday, told Reuters.

The IMF also estimated that there would be a $1 trillion global financing gap over the next two years if global economic conditions worsened considerably, the sources added.

The IMF currently has a lending capacity of about $380 billion. IMF sources said a European commitment to inject €150 billion into the IMF is included in the $600 billion estimate.

The new figures comes as G20 deputies from developed and developing nations gather in Mexico today for preliminary talks on boosting the IMF's war chest, with concerns growing that the euro zone debt crisis has worsened.

IMF managing director Christine Lagarde said yesterday she met with the IMF board to assess whether the- global lender needs additional funds to respond effectively to the euro zone crisis and said IMF management would explore options for increasing the Fund's firepower.

The IMF has warned it will cut global growth projections for 2012 when it updates its forecast on January 24th. Weakening global prospects raises fears that more countries will need rescuing by the IMF, especially if capital markets freeze up completely.

Efforts to prevent the looming threat of a Greek default will resume in Athens today as global banks return for fresh talks on how to break the deadlock over the second Greek bailout.

The rush to bring the Greek government and global banks together again, just five days after negotiators broke off talks on a private-sector contribution to the plan, underscores mounting anxiety over the threat of a default.

EU leaders have made the second EU-IMF rescue of Greece conditional on a big “haircut” for the banks and investment funds that hold Greek bonds, but seven months of negotiation have proved fruitless.

European shares and the euro got a boost today on talk the IMF may do more to help resolve the debt crisis but worries over the outcome of the Greek negotiations limited any gains.

The World Bank warned developing countries today to prepare for the "real" risk that an escalation in the euro area debt crisis could tip the world into a slump on a par with the global downturn in 2008 and 2009.

The World Bank predicted world economic growth of 2.5 per cent in 2012 and 3.1 per cent in 2013, well below the 3.6 per cent growth for each year projected in June.

It forecast high-income economies would expand just 1.4 per cent in 2012 as the euro zone shrinks 0.3 per cent, sharp downward revisions from growth forecasts last June of 2.7 per cent and 1.8 per cent, respectively.

It cut its forecast for growth in developing economies to 5.4 per cent for 2012 from its previous forecast of 6.2 per cent, saying expansion in Brazil and India and to a lesser extent Russia, South Africa and Turkey, had slowed already.

It saw a slight pick up in growth in developing economies in 2013 to 6 per cent. But the report said threats to growth are still rising, suggesting the outlook remained highly uncertain.

Elsewhere, Germany said today it economic growth to slow to 0.7 per cent this year before picking up to 1.6 per cent next year. It had previously forecast 2012 growth of 1 per cent.

In more positive news, a German sale of €3.44 billion of two-year bonds saw strong demand today as concerns over Greece led investors to stock up on safe-haven debt, while Portuguese treasury bills benefited from ample liquidity in the financial system.

Investors bidding for 2.2 times the amount of German bonds on offer despite the paper yielding just 0.17 per cent on average at the auction. That was lower than the 0.29 per cent yield at last month's auction.

Portugal easily raised €2.5 billion in a debt auction, just days after Standard & Poor's downgraded its credit rating to junk status.