(CNN) -- Responding to an allegation by the U.S. chairman of the Joint Chiefs of Staff that Pakistan's main intelligence agency has a "longstanding relationship" with a Taliban-allied insurgent group that targets U.S. troops in Afghanistan, a senior Pakistani intelligence official said: "We do have a relationship: that of an adversary." "We have made our resolve very clear that (the Haqqani Network) is an enemy we need to fight together," said the official, who did not want to be identified discussing intelligence matters. In an interview that aired Wednesday on Pakistan's Geo TV, Adm. Michael Mullen spoke forcefully about the Haqqani Network, which he said "very specifically facilitates and supports the Taliban who move in Afghanistan, and they're killing Americans."
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Adm. Mike Mullen said ISI has "longstanding relationship" with the Haqqani Network
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A senior Pakistani intelligence official says that relationship is "that of an adversary"
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"Onus of providing proof on this" rests with the Americans, the official says
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Despite strain, Mullen says leaders "are very committed to working our way through this"
"I also have an understanding that the ISI and the (@placeholder military) exist to protect their own citizens, and there's a way they have done that for a long period of time," Mullen said.