The US Secretary of Defence Robert Gates has arrived in Afghanistan on an unannounced visit. Mr Gates will hold talks with Afghan President Hamid Karzai and meet US troops serving in the country. Earlier, speaking to reporters on the flight to Kabul, Mr Gates said he will tell Afghan officials the US intends to be their partner for a long time. He said he will discuss with Mr Karzai the US decision to send further troops and how it will be implemented.Mr Gates is the most senior US official to visit Afghanistan after President Barack Obama announced he was deploying 30,000 extra US troops to the country.