International Monetary Fund director general Rodrigo Rato called on the world's key economic players to act jointly to address global imbalances, which he said have increased in the past six months. "Change of policies are not only needed in Asia but also in the US and Europe and .... one single change will probably have very limited effects," he told reporters. Rato called on the US to increase "in a very credible way" its rate of savings and to exercise budgetary restraint, and on the euro zone and Japan to increase their growth potential. He said Asia should move towards exchange rate flexibility. But he said a decision by China to revalue its currency would not in itself resolve the problem. "A more flexible exchange rate regime throughout Asia, and especially in China is certainly to the advantage of the Chinese economy and would also help to address global imbalances," he said. Rato said that while the downside risks have increased in the world economy, "there is reason to believe that the growth momentum could be recuperated in the second half of the year".