US President Barack Obama emphasised unity when he met the leaders of Pakistan and Afghanistan at the White House.The two countries arguably represent Washington’s most pressing foreign policy issue. Obama warned that all three countries must remain united in their fight against the Taliban and al Qaeda: “The road ahead will be difficult. There will be more violence and there will be setbacks. But let me be clear the United States has made a lasting commitment to defeat al Qaeda but also to support the democratically-elected sovereign governments of both Pakistan and Afghanistan. That commitment will not waver and that support will be sustained.” The US administration has sharply criticised both Hamid Karzai and Asif Ali Zardari in the past, questioning their commitment to and capability of tackling the threat from extremists. Meanwhile, the deaths of dozens of civilians in US air strikes on Taliban targets in Western Afghanistan cast a cloud over the talks. Local officials in Farah province say up to 100 people may have been killed. If that figure is confirmed, it would be one of the most serious incidents involving Afghan civilians since the fall of the Taliban in 2001.