The leaders of Pakistani and Afghanistan are meeting in Iran to discuss security as the battle against the Taliban intensifies in both countries.The talks are focusing on joint efforts to combat the insurgents, and the flourishing drugs trade that is helping to finance their campaign. It comes as Pakistan steps up an offensive against the Taliban in the Swat valley, with reports of street-fighting in the main town of Mingora. Regaining control of Mingora is said to be crucial to defeating the Taliban in Swat, and some 15,000 troops have been drafted into to complete the task. Washington, which has made winning the war in Afghanistan its top military priority, is backing the joint approach being taken by the three countries. To this end the Obama administration has sought to improve relations with Tehran in recent months, and has put pressure on Pakistan to tackle the Taliban in its own territory. But the battle is taking its toll on the civilian population in Swat. Some two million people are thought to have fled the fighting. Aid agencies say they are struggling to provide food and shelter for those who have been displaced.