China could be about to allow its currency to strengthen by as much as 5 percent to slow down the country's fast-growing economy, Goldman Sachs' chief economist was quoted as saying.

"I have a strong opinion that they're close to moving the exchange rate," Jim O'Neill says.

"Something's brewing. It could happen anytime," he recently told Bloomberg.

The news service said O'Neill believes China may allow the yuan to rise as much as 5 percent in a one-time revaluation and to then trade within a bigger band or against a larger basket of currencies.

"They need to do something to slow the economy down and deal with the inflation consequences," he was quoted as saying.

O'Neill believes China's economy is growing between 12 percent and 14 percent, Bloomberg said.

The World Bank has forecast China's economy will grow 9 percent this year, faster than global growth of 2.7 percent.

Beijing said it expanded by 8.7 percent in 2009.