FRANKFURT (AFP) - US Federal Reserve chief Ben Bernanke Friday hit back at opponents of US monetary policy at an appearance in Germany, one of the fiercest critics of measures to stimulate the weak American economy. Defending the recent decision to pump an extra 600 billion dollars into the financial system, Bernanke said US policy was not to blame for the current economic imbalances between advanced and developing countries. And the measures served to calm tensions on the markets and should promote growth, he said. In the short term, rebalancing economic growth between the advanced and emerging market economies should remain a common objective, as a two-speed global recovery may not be sustainable, he said. The countries of the world must recognise their collective responsibility for bringing about the rebalancing required to preserve global economic stability and prosperity. Bernanke was addressing a European Central Bank conference in Frankfurt, following sharp attacks on his policies by Germany, whose finance minister described as hopeless the Feds so-called quantitative easing. The US has already pumped endless amounts of money into the economy with extremely high budget deficits, and with a monetary policy which has already pumped in lots of money, Wolfgang Schaeuble said earlier this month. The results have been hopeless. But Bernanke said that the policy, essentially printing money as life support for the flagging US economy, had already eased financial market tensions and should spur growth. Financial conditions eased notably in anticipation of the (Fed) Committees announcement, suggesting that this policy will be effective in promoting recovery, he said. The Federal Reserve boss also went on the attack over currency policy, hitting back at those who argue the vast injection of cash is aimed at keeping the dollar low to boost exports. The dollars role as a safe haven during periods of market stress stems in no small part from the underlying strength and stability that the US economy has exhibited over the years, Bernanke said. The best way to continue to deliver the strong economic fundamentals that underpin the value of the dollar, as well as to support the global recovery, is through policies that lead to a resumption of robust growth in a context of price stability in the United States. In a thinly-veiled reference to China, accused of keeping its currency artificially low, he asked: Why have officials in many emerging markets leaned against appreciation of their currencies toward levels more consistent with market fundamentals? The principal answer is that currency undervaluation on the part of some countries has been part of a long-term export-led strategy for growth and development. However, such a tactic has demonstrated important drawbacks, both for the world system and for the countries using that strategy, he said. Bernanke spoke as a cornucopia of world finance leaders descended on Frankfurt for conferences, with the current eurozone debt crisis high on the agenda. Speaking at a separate conference, Greek Finance Minister George Papaconstantinou said that possible aid for Ireland would not be sufficient to calm turbulent bond markets in the 16-nation zone. Even if Ireland is helped, it cannot prevent the debt crisis from continuing, he said. He added the markets would turn their focus to other debt-wracked countries such as Spain and Portugal. Papaconstantinous remarks came as international financial experts and Irish officials began tough negotiations on a possible bailout for the debt-ridden economy. Also expected to speak in Frankfurt later Friday were International Monetary Fund chief Dominique Strauss-Kahn, European Central Bank President Jean-Claude Trichet and the head of the German central bank Axel Weber.