NEW DELHI: In a clear indication of the Obama administration 's scepticism about Pakistan 's anti-terror efforts, the highest ranking officer in the United States armed forces has accused Islamabad's Inter-Services Intelligence ( ISI ) agency of having ties with terrorists.The US Joint Chiefs of Staff Chairman, Admiral Mike Mullen , told a Pakistan TV channel that "ISI has a long standing relationship with the Haqqani network". He said he was going to raise this issue with Pakistan Army chief General Ashfaq Kayani and other leaders."I believe over time that's got to change and that's the kind of focus I try to bring in my discussions with General Kayani and other leaders," Admiral Mullen said.Admiral Mike Mullen made the remarks after touching down in Islamabad for discussions with Pakistan's top general to address concerns over official links with militants in the region."It is well known that ISI had a relationship with the Haqqani network, and addressing the Haqqani network from my perspective is critical to the solution set in Afghanistan. ... that's at the core - it's not the only thing - but that's at the core that I think is the most difficult part of the relationship," the Dawn quoted Admiral Mullen, who is quite often criticised for being soft on the Pakistan military, as saying in the interview.He also made it clear that ISI's relationship with the terror network was unacceptable to the American leadership. "The ISI has a rich history of how they operated in this part of the world, to protect their own country. I understand that some of the aspects of that we strongly disagree with and that is something that we continue to address," said Admiral Mullen.The Haqqani network had fuelled the Afghan insurgency by supporting, training and funding fighters who were killing US and coalition troops in Afghanistan. Admiral Mullen depicted a destabilising scenario in which terror groups such as the Lashkar-e-Taiba (LeT), the Jamaat-ud-Dawa (JuD), the Al Qaeda and the Haqqani network would become increasingly interlinked.Credible intelligence with the Indian government has it that LeT has in fact become the principal dispenser of instructions from Pakistan on Indian targets. Pakistan's army-ISI establishment continues to direct operations and even pay for the attacks while LeT is in charge of executing the attacks. Even though there has been no major attack against Indians in recent months, the attempts by Pakistan-sponsored LeT are relentless.Meanwhile, rubbishing the claims of Admiral Mullen, Pakistan labelled his statement as one of 'negative' propaganda. Pakistan Army Chief General Ashfaq Parvez Kayani hit back stating that his army is consistently working to defeat terrorism "I strongly reject negative propaganda of Pakistan not doing enough. Pakistan's Army's ongoing operations are a testimony of our national resolve to defeat terrorism." reports from Islamabad quoting Gen Kayani said.