The role of the U.S. dollar as the key global currency will decline after the financial crisis, and its value may also weaken due to America's current account deficit, officials at some of Asia's top think tanks said.

The dollar's role will gradually be shifted, Zhang Yunling, director of Institute of Asian and Pacific Studies at Chinese Academy of Social Sciences, told a news conference in Tokyo after a meeting of Asian research groups.

China hopes to have a stable and gradual transition rather than a radical revolution, he added.

The dollar logged its biggest daily fall against a basket of currencies in more than two decades on Wednesday as the U.S. Federal Reserve said it would buy long-term Treasuries.

The Fed move stirred worries that the U.S. would spew dollars into global markets, leading to an oversupply of the world's main reserve currency.

Chalongphob Sussangkarn, a former Thai finance minister and now president of Thailand Development Research Institute, also expressed worries about any sharp fall in the dollar.

The U.S. deficit is so huge. This is why all countries, particularly East Asia, are concerned because we hold a lot of these assets. What happens if the U.S. dollar falls 40 percent? Many central bankers will be losing huge amounts of money.

The officials also called on East Asian leaders attending next month's G20 summit in the UK to avoid competitive currency depreciation as a way to escape from the current crisis.

(Reporting by Yoko Nishikawa; Editing by Kim Coghill)

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