Nov. 8 (Bloomberg) -- BHP Billiton Ltd., the world's biggest mining company, said it offered to buy rival Rio Tinto Group, a proposal that was rejected.
BHP, based in Melbourne, said in a statement to the Regulatory News Service it ``recently'' wrote to the Rio board with an outline plan for a merger. BHP has again written to Rio to try to arrange a meeting. Rio stock rallied as much as 25 percent in London, while the company has a current market value of $161 billion.
``The boards of Rio Tinto have given the proposal careful consideration and concluded that it significantly undervalues Rio Tinto and its prospects,'' Rio said in a separate statement. ``The boards have unanimously rejected the proposal as not being in the best interests of shareholders.''