The International Monetary Fund, in a report summarizing its assessment of potential spillover impacts of global economic policy, suggested on Friday that debt sustainability was a key area of concern.

The global lender provides so-called Article IV assessments of member countries' individual economies but decided to extend the analysis to gauge how developments in one key region might affect, or spill over, into other regions.

It looked at the United States, European Union, China, Britain and Japan, all of which have large volumes of trade with one another as well as extensive financial linkages including through globally operating banks.

One of its findings was that there was a significant regional impact from growth spillovers, so that Japanese shocks most affect China and vice versa while euro zone shocks matter more to Britain, implying the importance of trade and supply chain disruptions as potential adverse influences.

Only the United States seems to matter profoundly to everyone, although it too matters most to Canada and Mexico, the IMF noted.

A key way in which spillovers are felt is through financial markets when, for example, stress in one country's economy pushes up others' bond yields and can affect currency values.

The IMF notes that current efforts to rein in U.S. indebtedness could trigger spillover effects elsewhere.

Were the current path of fiscal policy to lead to a loss in confidence in sovereign debt sustainability, the consequences for the rest would be enormous, the report said.

Similarly, if financial stresses in peripheral euro zone countries such as Greece spread to core euro area banks, the hit to banks across the world in terms of risk premia would in many cases rival that from the Lehman event in 2008.

Lehman's bankruptcy in 2008 at the height of the 2007-2009 financial crisis wracked both stock and bond markets, sending shockwaves throughout the global financial system.

The IMF said it was unclear yet whether the spillover reports will become a useful surveillance tool for the fund but it is going to continue conducting them in 2012 though it has not yet decided which countries it will look at.

Finance ministers and central bankers meeting in Washington at the IMF and World Bank semi-annual meetings this month will discuss the main findings of the spillover reports, the IMF said.

(Reporting by Glenn Somerville; Editing by James Dalgleish)

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