HONG KONG, Feb 6 Reuters - The Hong Kong-listed shares of Aluminum Corp of China Ltd, or Chalco, fell 9.5 percent on Wednesday after BHP Billiton made a bid for Rio Tinto . Chalco's parent company Chinalco has taken a 9 percent stake in Rio shares, together with its partner Alcoa Inc. , and has said it reserves the right to react to a bid for Rio by BHP by making an offer of its own for the firm. But credit rating agencies have warned that Chalco's creditworthiness could suffer from Chinalco's investment. Standard & Poors said late on Tuesday it had put Chalco on creditwatch negative. "The CreditWatch placement reflects Standard & Poor's expectation that the large debt burden on Chinalco will put downward pressure on Chalco's financial profile," said Standard & Poor's credit analyst Xiaoming Song in a statement.
