Even assuming that the IMF took some of the strain of such rescues, the increase in the implied indebtedness of Germany of rescuing both Italy and Spain would be in the order of well over 10% of its GDP or output.

BBC: Eurozone nations�� sovereignty v AAA

"This increase is putting a large strain on public finance, " says Kawai of the World Bank.

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If the cost of mortgages were to rise because of an increase in interest rates, household incomes would be put under even more strain.

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It is widely believed that using guarantees to increase the firepower of the EFSF in either of these ways would impose so much additional strain on France's public-sector balance sheet that France is likely to lose its cherished AAA rating - which would then make the eurozone even more dependent on the financial strength of Germany.

BBC: Eurozone banks to raise more than 100bn euros

As for the creation of a eurozone federation, during the implementation phase the perceived strain on German public finances would increase.

BBC: Eurozone nations�� sovereignty v AAA