In an address to the American Chamber of Commerce and U. S.-China Business Council, US Commerce Secretary Gary Locke said on Wednesday that the trade imbalance between the United States and China is not sustainable. He called for a more flexible exchange rate for accelerating the recovery of the global economy.

Locke remarked: "For all our areas of agreement, the United States and China's trade relationship has to evolve. There are concerns and deep structural issues that must be addressed. Chief among them is a bilateral trade imbalance that simply can't be sustained. Growth predicated on ever increasing Chinese exports being consumed by debt-laden Americans provided years of prosperity - but it also sowed some of the seeds for our current economic problems."

Though Locke praise China's endeavors to stimulate the national economy, he added a flexible exchange rate and further opening up of Chinese markets for imports and foreign direct investments would help the global economy.

Along with stressing on measures to improve the trade imbalance, Locke - who is preparing for his first trip to China, with US Energy Secretary Steven Chu - intends promoting clean energy technology as a key area wherein US industry can explore opportunities in China. He said that it was imperative the US and China team up for the reduction of greenhouse gases that cause global warming.