As the banking regulator ratchets up the pressure on the big four banks to raise billions of dollars to make them more resilient, analysts are predicting Commonwealth Bank of Australia and ANZ Banking Group will be forced to strengthen their balance sheets to avoid slipping behind rivals. The Australian Prudential Regulation Authority said the big four banks would have to raise 2 percentage points of capital - around $28 billion - to make them "unquestionably strong", as recommended by the financial system inquiry led by David Murray.