Afghanistan President Hamid Karzai said recent leadership change in Pakistan has offered for the "first time" a hope of winning the "war on terror" and called for a joint assault on extremist "sanctuaries" along their common border. He also asked the United States to provide full backing to the new democratically elected administration of President Asif Ali Zardari, who took over from former military strongman Pervez Musharraf, in fighting extremism. Relations between the neighbors were strained during Musharraf's rule, with the Afghan leader persistently accusing Islamabad of not doing enough to curb cross-border militancy. "For the first time, I see in the region a ray of hope," Karzai said at a New York-based Asia Society forum on the sidelines of the UN General Assembly. He said Zardari, whose wife former prime minister Benazir Bhutto was killed in a suicide blast, would move away from what he charged was Islamabad's longstanding use of "radicalism and extremism as an instrument of policy." "If we can all work together, Afghanistan, Pakistan, the United States and our allies, I see now possibilities of moving beyond the days where one or the other of us may need extremism or radicalism as an instrument of policy and when that happens, there would be no place for extremists to play against all of us and if that happens, there will be no extremist activity as it is now."