United States Defence Secretary Donald Rumsfeld has acknowledged the difficulty of combating global terrorism. He was speaking during a visit to Afghanistan, which has seen a resurgence of activity by suspected Taleban fighters and their supporters. Coalition forces faced a complex task in trying to defeat groups that operated across borders, Mr Rumsfeld said in Kabul. \"The global war on terrorism isn\'t a problem in or for one country,\" he said. But Mr Rumsfeld said US forces in Afghanistan had told him they were having success in countering attacks by supporters of the ousted Taleban. This is set to be used to demobilize militias that support the Taleban, speed up the deployment of provincial reconstruction teams and step up the training of an Afghan national army. Mr Rumsfeld and Mr Karzai met to discuss efforts to rebuild the country, and the threat posed by militia groups. At a news conference afterwards, both stressed the importance of rebuilding Afghanistan\'s infrastructure and Mr Rumsfeld assured Afghans of continued American support. Before arriving in Kabul, Mr Rumsfeld flew to a remote US base in Gardez, south of the capital, where 80 American soldiers are stationed. They are involved in tackling militia fighters and are also helping with reconstruction projects, such as repairing schools, opening roads and digging wells The Afghan capital was under tight security blanket for Mr Rumsfeld\'s visit, with extra roadblocks set up at key points in the city. Hours before the defense secretary\'s arrival, suspected Taleban fighters fired rockets at a local administrative office in the troubled province of Paktika, along the Pakistan border. (BBC)