The nine-year war in Afghanistan has reached a critical stage, U.S. General David Petraeus said Sunday, as he formally took command of the 150,000-strong NATO-led force fighting a deadly Taliban insurgency. "We are engaged in a tough fight. After years of war we have arrived at a critical moment," Petraeus told guests at a change-of-command ceremony at the NATO-led International Security Assistance Force (ISAF) headquarters in Kabul. Petraeus was last week appointed to lead all foreign forces in Afghanistan after his predecessor, General Stanley McChrystal, was dismissed for insulting remarks he and aides made about the U.S. administration in a magazine interview. The change of command comes at a time when the Taliban are at their strongest since being overthrown in 2001, with ISAF casualties mounting daily. Petraeus, wearing camouflage fatigues and speaking near a marble column dedicated to ISAF forces who have died in the Afghan campaign, said his appointment signaled a change in command, not strategy. Petraeus landed in Kabul Friday after his appointment was confirmed by the Senate and the 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'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 is charged with not only winning the war against a growing Taliban insurgency, but also with starting a withdrawal of U.S. forces from July next year. "We must demonstrate to the Afghan people and to the world that al Qaeda and its network of extremist allies will not be allowed to once again establish sanctuaries in Afghanistan," he said.