The United States' top field commander, General David Petraeus, warned on Saturday of a tough mission ahead a day after arriving to take command of the 150,000-strong NATO-led foreign force in Afghanistan. Petraeus told hundreds of guests at a U.S. embassy party held to mark US independence day that it was essential to show unity of purpose to solve Afghanistan's problems. “This is a tough mission, there is nothing easy about it,” he said at the sprawling and heavily fortified US embassy complex in Kabul, Washington's biggest foreign mission anywhere in the world and boasting 5 ambassadors. Petraeus is charged with not only winning the war against a growing Taliban insurgency, but also with starting a withdrawal of US forces from July next year. Wearing casual camouflage under a scorching Kabul sun, Petraeus and a besuited U.S. Ambassador Karl Eikenberry on Saturday welcomed scores of guests to an embassy compound liberally decorated with Stars and Stripes flags. A brass band played as guests munched on burgers, corn-on-the-cob, popcorn and ice-cream cones. Petraeus's appointment could be a last throw of the dice for Washington to end an increasingly costly conflict that is draining Western budgets as they emerge from one of the worst global recessions in history. He landed in Kabul on Friday after his appointment was confirmed by the US Senate and the US House of Representatives approved $33 billion in funding for a troop surge he hopes will turn the tide of the war. The surge will bring to 150,000 the number of foreign troops in Afghanistan just as a new strategy takes root. It entails tackling the Taliban in their strongholds while relying on the government to simultaneously improve local governance and development. Petraeus, who is due to formally take command at a ceremony at the International Security Assistance Force (ISAF) headquarters on Sunday, is credited with turning the tide of the war in Iraq using similar tactics. ISAF said on Saturday that a service member had died in an improvised explosive device (IED) attack in the south.