ISLAMABAD (Agencies) Pakistan army chief Gen Ashfaq Pervez Kayani cancelled a Monday visit to Britain where he was to meet privately UK Defence Minister Liam Fox. Chief of the Army Staff (COAS) Gen Kayani was also scheduled to address the International Institute for Strategic Studies and the Royal College of Defence Studies. Britains Ministry of Defence confirmed that the visit has been cancelled but declined to speculate on why Gen Kayani scrapped it. A Pakistani official said Gen Kayani was staying in Pakistan to hold talks on the crisis sparked by the US accusations against Pakistans spy agency, Inter-Services Intelligence (ISI). Tensions have escalated between Islamabad and the United States over security after Washingtons allegations that Pakistani spies helped insurgents attack American targets in Afghanistan and that the terror war ally was pursuing a 'policy of 'exporting terrorism to her war-ravaged neighbour, charges vehemently denied by Islamabad. Last week, the chairman of the US Joint Chiefs of Staff, Admiral Mike Mullen, accused the ISI of having backed Afghan insurgent group Haqqani network in the planning and execution of a Sept 13 assault on the US Embassy in Afghanistan as well as a truck bomb that wounded 77 American soldiers days earlier. Pakistan Army and government have dismissed the allegations as baseless. But a Republican on the Senate Armed Services Committee has said the US should consider military action as an option against Pakistan if it continues to support terrorist attacks against Americans in Afghanistan. Senator Lindsey Graham also said assistance to Pakistan should be reconfigured, and that the US should no longer designate an amount of aid for Pakistan but have a more transactional relationship with the country. Relations between the US and Pakistan have been strained since the US forces killing of al-Qaeda leader Osama bin Laden in a clandestine unilateral raid Abbottabad town of Pakistan in May, invoking a sharp and widespread reaction in the country that deemed it an attack on her national sovereignty. Days after Mullens accusations, Gen Kayani held an extraordinary meeting of his commanders on Sunday in Islamabad. Holding a Corps Commanders moot, reported to be longest-ever and possibly for the first time on a Sunday, reflected the seriousness of the crisis. Without giving any details of the meeting, ISPR spokesman Major-General Athar Abbas said: The prevailing security situation was discussed. However some military sources said that meeting rejected all the allegations and expressed its concern over the negative statements emanating from the US. The meeting reiterated that Pakistan Armed Forces were committed to achieving enduring peace in the region and expressed total resolve to give befitting response in case there was any effort to violate national sovereignty. The Haqqani network is the most violent and effective faction among Afghanistans Taliban fighters. Pakistan officially withdrew support for the Taliban after the September 11 attacks on the United States in 2001 and allied itself with Washingtons war on terrorism. Gen Ather, however, acknowledged that ISI maintained contacts with the Haqqanis, but said that didnt mean it supported it. No intelligence agency can afford to shut the last door of contact, he told Reuters on Sunday. Maintaining contact doesnt mean that you are endorsing or supporting that terrorist organisation. Separately on Sunday, General James N Mattis, the US central command (CENTCOM) commander, met Khalid Shameem Wynne, chairman of Pakistans Joint Chiefs of Staff Committee, who expressed concern over the negative statements emanating from [the] US. He [Wynne] stressed upon addressing the irritants in relationship which are a result of an extremely complex situation, the military said in a statement He reiterated that Pakistan armed forces are committed to achieving enduring peace in the region which will only be possible through mutual trust and co-operation. Pakistans Foreign Minister Hina Rabbani Khar Monday repeated her assertion that faced with a defeat in Afghanistan the US was trying to make Pakistan a scapegoat. Shaukat Qadir, a retired Pakistani brigadier, said the US was having difficulty defeating terror networks. The fact is the US in Afghanistan is failing. I think that fact is pretty obvious to everybody, he told Al Jazeera. Prime Minister Yousuf Raza Gilani spoke to political leaders by telephone on Sunday and decided to call an all-party meeting to discuss the issue of tensions with the US. Gilani rejected the allegations as a sign of US confusion and policy disarray.