BEIJING (Reuters) - China should gradually reduce its holdings of U.S. debt and can stop buying dollar-denominated bonds, a Hong Kong newspaper on Tuesday quoted Cheng Siwei, a vice chief of China's parliament, as saying. With China a leading financier of the U.S. current account deficit, Cheng's comments sent the dollar lower against the euro and yen and also pushed down prices of U.S. government bonds. The Beijing-funded Wen Wei Po daily carried Cheng's comments, made in Hong Kong on Monday, but it was not immediately clear whether they reflected those of top decision makers who determine the content of...