Singapore Telecommunications Ltd. Will "aggressively" defend its sagging local mobile phone market share from competition, saying it won't allow its share to fall below 40 percent. The company's executive vice president, Lim Chuan Poh, said the company would take steps to prevent rivals MobileOne Ltd. and StarHub Pte. Ltd. from gaining further ground. "I think 40 percent would be the line where we would be defending aggressively," said Mr. Lim, who is also chief executive of SingTel Mobile.