Jitters about Greece’s ability to cope with its massive debt burden swept through global sharemarkets overnight, as Greek banks turned to the government to help them cope with a flight of capital.

Greece’s finance minister, George Papaconstantinou, confirmed that Greece’s four largest banks had requested access to the funds that remained in the $US37 billion ($A39.9 billion) government scheme aimed at helping the banks weather the 2008 financial crisis. Just under $US23 billion of the package is left, mainly consisting of loan guarantees and special bonds that could be used to borrow from the European Central Bank.

Wealthy individuals and companies have shifted an estimated $14 billion of deposits — or just under 5% of all deposits in the Greek banking system — out of Greece in the first two months of this year. Greek banks have also found their access to international capital markets have become restricted as commercial lenders have become increasingly wary of accepting Greek bonds as security for loans — even for short-term loans.

As a result, Greek banks have become increasingly dependent on the ECB for funding, because the bank still accepts Greek bonds as security for loans.

Greece’s funding difficulties are intensifying. Greek interest rates continued to climb overnight, with the yield on the benchmark 10-year bond edging up to 7.13%, the highest in more than a decade.

At the same time, Mohamed El-Erian, the co-chief investment officer and chief executive of PIMCO, the world’s largest bond fund, warned: “It is likely that things will get worse for Greece before they get better.”

In an article published in the Financial Times, El-Erian predicted that in the near term “the persistence of alarming risk spreads will lead to even more cautious behaviour among depositors and investors. Late movers will sell Greek assets rather than buy them, putting even greater pressure on the government’s ability to raise sustainable funding for its forthcoming debt maturities in May.”

El-Erian thought it likely that the blame game between Greece and its European neighbours would likely worsen, with Greece blaming the eurozone countries for not providing more support, while they, in turn, would emphasise the need for increased Greek austerity. Markets, he said, had failed to appreciate the difficulties in resolving Greece’s debt problem.

“When they do, it will also become apparent that Greece is part of a wider, and historically unfamiliar phenomenon — that of a simultaneous and large disruption to the balance sheet of many industrial countries. Tighten your seat belts.”

Meanwhile, concerns about government debt reverberated in the United States, with Federal Reserve chairman Ben Bernanke warning the country needed to come up with a credible plan for tackling government budget deficits.

In a speech given in Dallas, the Fed chief warned that “unless we as a nation demonstrate a strong commitment to fiscal responsibility, in the longer run we will have neither financial stability nor healthy economic growth.”