US commander in Pakistan warning

A US troop build-up in Afghanistan could push Taliban fighters deeper into Pakistan, further destabilising it, the most senior US commander has warned.Admiral Michael Mullen, who chairs the Joint Chiefs of Staff, was speaking at a meeting of the Senate Foreign Relations Committee in Washington.Thousands of Pakistani troops are already battling Taliban militants in the north-west of the country.Up to two million people in the area have fled the fighting, the UN says.