WASHINGTON - Asserting that Pakistan is not a failed state, US Presidents special envoy for Pakistan and Afghanistan Tuesday gave President Asif Ali Zardari a much-needed boost on the eve of the tripartite summit here as the Pakistani military stepped up its assault against the Taliban. We have not distanced ourselves from President Asif Ali Zardari - the US should unambiguously support the democratic Pakistan led by democratically-elected Pakistani President, Holbrooke told a congressional committee, rejecting media reports that Obama Administrations confidence in the Pakistani leader was waning. Last week, The New York Times, citing senior administration officials, said one move being discussed was to reach out to PML-N chief Nawaz Sharif, Zardaris main rival. Holbrooke said the US maintains contacts with the Opposition political parties in Pakistan, as it does in other countries, including with Nawaz Sharif and Shahbaz Sharif. We have the highest strategic interests in supporting this government (of Pakistan), he underscored, saying both the US and Pakistan have common goals in the fight against violent extremism. Pakistans survival as a moderate, democratic state is critical to US national security, Holbrooke said. Our most vital national security interests are at stake, he told the House Foreign Affairs Committee. Holbrooke was testifying ahead of meetings this week between President Barack Obama and the leaders of Afghanistan and Pakistan during which the Administration is expected to press the Pakistanis on combating extremists. US officials regard Pakistans role as key to the success in Americas escalating military operation in Afghanistan. We need to put the most heavy possible pressure on our friends in Pakistan to join us in the fight against the Taliban and its allies, Holbrooke said. We cannot succeed in Afghanistan without Pakistans support and involvement. He told lawmakers that we should not confuse this (support) with prediction of collapse (of the Pakistani state). Pakistan is not a failed state, he said, negating doomsday scenarios painted in the media. Pakistan, he said, is facing challenges but is not in a situation where it could collapse. Congressman Howard Berman chaired the hearing of the influential committee. The special representative noted that relations between the US and Pakistan have been inconsistent over the years. In Pakistan, many believe that we are not a reliable long-term partner and that we will abandon them after achieving our counter-terrorism objectives. Many in the US question the dedication of some elements of the Pakistani government to ending safe haven for terrorists on Pakistani soil. But our engagement has to be aimed at putting our relationship on a better long-term footing. He said in order to assure a strong partnership in the fight against extremists, constancy and consistency must be the hallmarks of our engagement with Pakistan. This engagement must be conducted in a way that respects and enhances democratic civilian authority while also engaging the Pakistani people in our commitment to help them pursue a prosperous economy, a stronger democracy, and a vibrant civil society. Agencies add: US special envoy Holbrooke, in his testimony, feared that Taliban could flee to Balochistan from the tribal areas. He vowed unambiguous backing President Zardari despite mounting disquiet in Congress. Security assistance for Pakistan has to show results, he added, suggesting that the US may tie an increase in aid to Pakistan to benchmarks in a variety of areas but it would not be correct to impose tough conditions. The administration intends to implement measures of performance in its economic, social and military assistance to Pakistan, he said, saying such conditions must not worsen the 'trust deficit that plagues US-Pakistani relations. Any attempt by the Pakistan Army to launch a coup against Zardaris eight-month-old civilian government would be terrible, he added in testimony to the House of Representatives. Wednesdays (today) summit gathering of US President Barack Obama, Zardari and Afghan President Hamid Karzai was historically important, he told restive lawmakers. The US envoy sought to tamp down speculation that the Obama Administration was seeking to distance itself from Zardari. He said Pakistan was of vital strategic interest to the US both to help stabilise Afghanistan and to prevent either country from becoming a springboard for attacks on the United States. Pakistans of such immense importance to the US, strategically and politically, that our goal must be to support unambiguously and help stabilise a democratic Pakistan headed by its elected President, Asif Ali Zardari, Holbrooke said. We have the highest strategic interest in supporting this government, he said, noting that Zardari had ordered a military offensive in the Swat region as a controversial peace deal with the Taliban breaks down. Rejecting US media reporting that President Barack Obamas Administration is reaching out behind Zardaris back to political rival Nawaz Sharif, he added: We think it is a state that is under extreme test. We have the same common enemies, said Holbrooke. He said the US Administration had absolutely no interest in seeing the Pakistani military return to power in place of Zardaris shaky government. We are strongly opposed to any such event. We have made that unambiguous and made it clear to all parties, publicly and privately, Holbrooke said. We think this would be a terrible event. Ratcheting up pressure on Pakistan to take on Taliban whose influence is spreading in the nuclear-armed country, the US envoy said the country must demonstrate its commitment to defeating Al-Qaeda and other militants on its soil. Pakistan must demonstrate its commitment to rooting out Al-Qaeda and the violent extremists within its borders, he said. Al-Qaeda leader Osama bin Laden plotted the Sept 11 attacks on the United States from Afghanistan, where he was sheltered by a Taliban regime that the US-led forces toppled in late 2001. US lawmakers voiced their deep worries about Pakistan during the hearing, sometimes it remarkably blunt terms. We cant allow Al-Qaeda or any other terrorist group that threatens our national security to operate with impunity in the tribal regions of Pakistan, House Foreign Affairs Committee Chairman Howard Berman, a Democrat, said at the hearing. Nor can we permit the Pakistani state - and its nuclear arsenal - to be taken over by the Taliban, Berman added. Representative Gary Ackerman, also a Democrat, said: Pakistans pants are on fire. He then launched into a scathing criticism of Pakistani President Asif Ali Zardari and other Pakistani officials. President Zardari has said the right things ... but in practice his governments response has been slow, weak and ineffective, Ackerman added. The fire is real and they need to respond. Meanwhile, US special envoy Richard Holbrooke called on President Asif Ali Zardari and informally discussed relationship between the two countries. Holbrooke warmly welcomed President Zardari on behalf of US President Barack Obamas Administration, Information Minister Qamar Zaman Kaira told reporters. Earlier, President Zardari also had a meeting with his advisors to devise and firm up Pakistans position on various issues that are likely to come up at the meetings during the visit.