BEIJING -- China is not manipulating the yuan for exports, said Ministry of Commerce spokesman Shen Danyang on Tuesday.

Exchange rates are not a major factor affecting or determining trade imbalances between China and the United States, he said.

China has been reforming its exchange rate system and expanded the floating rang in March, bringing more fluctuation, Shen said, adding that many factors have contributed to the results, for example, the limits set by the Unites States on its exports to China.

The ratio of US high-tech exports to China against China's total imports of similar products dropped to 8.6 percent in 2013 from 18.3 percent in 2001, Shen said.

The yuan has appreciated 10.1 percent this year against the euro, 10.8 percent against the yen and 4.2 percent against the pound sterling. The yuan's real effective exchange rate rose 2.37 percent in the first ten months.

Shen made the remarks at a monthly press conference, in response to a statement by William Reinsch, vice-chairman of the United States-China economic and security review commission, that China had lowered its yuan exchange rate to boost exports.

The congressional commission was set up in October 2000 to monitor and investigate national security and trade issues between the United States and China.