President George W Bush has said that he was sending a message of protest to Beijing at the alleged involvement of Chinese workers in helping Iraq to improve its air defence facilities. Reports say that Chinese personnel have been upgrading the country's military communications network with fibre optic cable. Mr Bush's comments came as American aircraft attacked targets in northern Iraq for the second time in recent days. Mr Bush outlined his administration's policy towards Iraq and said that he wanted to make it clear to President Saddam Hussein that Baghdad must behave peacefully.