(CNN) -- The U.S. ambassador to Islamabad was summoned to Pakistan's Foreign Ministry on Saturday, a day after Pakistan Taliban leader Hakimullah Mehsud was killed by a U.S. drone strike. Foreign Ministry spokesman Aizaz Ahmed Chaudhry did not explain why the envoy was summoned. A U.S. State Department official confirmed the meeting to CNN but would not disclose details about it. The State Department official would not discuss U.S. operations in Pakistan but stressed the Pakistan Taliban's 2009 attack on a U.S. base in Afghanistan and claims of responsibility for a failed attempt to bomb Times Square in New York.
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NEW: U.S. official stresses Pakistan Taliban ties to 2009 attack and Times Square plot
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U.S. and Pakistani officials say Taliban leader Hakimullah Mehsud died in a drone strike
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Haqqani terror group vows attacks within a few days
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Government peace talks with the Pakistan Taliban will not be delayed, minister says
But reports that he was alive surfaced in April of that year, and in May 2010 he appeared in a video in which he vowed attacks on major @placeholder cities.