It will take about 10 years for the renminbi to be internationally accepted as a common currency, said a former government official in his new book.

Cheng Siwei, former vice-chairman of the Standing Committee of the National People's Congress, outlined three prerequisites for renminbi internationalization: exchange rate reform, free exchange of the currency, and the opening up of the capital account.

Cheng suggested two "flexible exchange rate ranges", one determined by the demand and supply in the market, the other open to intervention by the currency authorities if necessary.

In terms of the opening up of the capital account, Cheng proposed that the long-term capital flow and foreign direct investment should be first opened, followed by short-term capital flow and foreign indirect investment.

He also urged the convertibility of renminbi under the capital account.