WASHINGTON - Nuclear-armed Pakistan is becoming a mortal threat to the world, US Secretary of State Hillary Clinton told the House Foreign Affairs Committee Wednesday. Pakistan poses a mortal threat to the security and safety of our country and the world, Hillary Clinton said. And I want to take this occasion ... state unequivocally that not only do the Pakistani government officials, but the Pakistani people and the Pakistani diaspora ... need to speak out forcefully against a policy that is ceding more and more territory to the insurgents ... . (We) cannot underscore the seriousness of the existential threat posed to the state of Pakistan by the continuing advances now within hours of Islamabad that are being made by a loosely confederated group of terrorists and others who are seeking the overthrow of the Pakistani state. I dont hear that kind of outrage or concern coming from enough people that would reverberate back within the highest echelons of the civilian and military leadership of Pakistan, she added. In her first testimony to Congress since her confirmation as the US chief diplomat in January, Hillary also defended President Barack Obamas overtures to Cuba, which has been under a broad US economic embargo for decades. She sought to reassure Howard Berman, Chairman of the House Foreign Affairs Committee, who backed a new dialogue with Iran but asked if Washington could garner enough support to impose crippling sanctions if it failed. She said the administration has more leverage with other nations through its negotiations with the other four UN Security Council members - Russia, China, France and Britain - plus Germany. The fact that we have been willing to go even beyond the P5-plus-1 and to reach out to Iran, to invite them, as I did, to the conference in The Hague on Afghanistan increases even further our ability to ask more from other nations, she said. We are more than willing to reach out to the Iranians to discuss a range of issues, assuming theyre willing to reach back, she said. But we are also laying the groundwork for the kind of very tough, I think you said crippling, sanctions that might be necessary in the event that our offers are either rejected or the process is inconclusive or unsuccessful, she said. In her testimony, the chief US diplomat urged Pakistani government officials as well as Pakistanis at home and abroad, including in the United States, to speak out forcefully against a policy that is ceding more and more territory to the insurgents. She sought to underscore the seriousness of the existential threat posed to the state of Pakistan by the continuing advances, now within hours of Islamabad, that are being made by the Taliban and others. The chief US diplomat recalled that such militants are dangerous because they are seeking the overthrow of the Pakistani state, which as we all know is a nuclear armed state, she said. She also defended US efforts to improve ties with Cuba as the country faces a transition. You can see there is beginning to be a debate, Hillary said, referring to differences between President Raul Castro and his older brother, Fidel, the ailing longtime leader, over Obamas overture. I mean this is a regime that is ending. It will end at some point, Clinton said. Agencies add: The Pakistani government was basically abdicating to the Taliban in agreeing to the imposition of Islamic (Sharia) law in part of the country, US Secretary of State Hillary said, strongly criticising Islamabad for the deal with the Taliban. She testified before the House Foreign Affairs Committee, where Chairman Howard Berman told her the panel is concerned about extremists gaining momentum in Pakistan. Berman, a Democrat, said the US couldnt allow the extremists to take over Pakistan or to operate with impunity on Afghanistans border. Hillary asserted in response that the international community was working closely together to address the problem of extremism in both Afghanistan and Pakistan. She noted that the risks were particularly heightened by the existence of Pakistans nuclear arsenal, which many analysts are concerned might fall into the hands of extremists should the central government be overthrown. I think that the Pakistani government is basically abdicating to the Taliban and to the extremists, Hillary told lawmakers when asked about the introduction of Sharia the Swat Valley under a deal to end Taliban violence. Later she said the administration believes the Pakistani government shares U.S. goals in defeating terrorism. On Indian, US Secretary of State Hillary said advancing of relationship with New Delhi, which was the worlds largest democracy and a key ally, was essential for the Obama Administration. Earlier in his introductory speech Howard Berman, Chairman of the Committee, said he was encouraged by the improving ties between New Delhi and Washington. Meanwhile, the United States is concerned by the expansion of the Taliban in Pakistan, a senior State Department official said Wednesday after the Taliban moved closer to Islamabad. This latest move is of concern to us, the official told AFP on the condition of anonymity. But we continue to work with the government of Pakistan to counter Taliban and other violent extremists operating in both Pakistan and Afghanistan. Pakistani officials said Wednesday that Taliban in the Swat Valley have moved into another district in a bid to broaden their control despite a deal designed to end extremist violence. Hundreds of armed Taliban from the scenic northwestern valley have entered Buner district, only 110km from the capital Islamabad.