Afghanistan: Pakistan urges U.S. to tread carefully in Afghan withdrawal --- (Reuters) - A senior Pakistani official urged the United States on Monday to ensure the U.S. military withdrawal from Afghanistan does not leave a vacuum that threatens regional stability and Pakistan's own security. -- "Although the war in Afghanistan may be winding down, just as in the past, Pakistan will have to face the brunt of any instability that may engulf Afghanistan after 2014," said Sartaj Aziz, Pakistan's national security and foreign affairs adviser. -- Aziz and U.S. Secretary of State John Kerry delivered prepared remarks before opening discussions in Washington that are part of a 'strategic dialogue,' which have sought to move bilateral relations beyond crisis-driven security concerns to cooperation on trade, energy and education. -- The United States has long said that violence in its long war in Afghanistan has been driven in part by militants' ability to rest and resupply in western Pakistan. American ties with Pakistan have been further strained by U.S. drone strikes against militants in Pakistan. -- Kerry paid tribute to the high price Pakistan has paid in fighting extremism. -- "I think few have suffered more at the hands of terrorists and extremists than people in Pakistan," Kerry said. --- With violence in Afghanistan continuing, including a January 17 suicide bombing that killed 21 civilians at a Kabul restaurant, the future of the U.S. and NATO presence in Afghanistan remains uncertain.--- Aziz said the United States should consider Pakistan's security when making its next moves in Afghanistan, something he said Washington did not do when withdrawing troops from Afghanistan in the early 1990s or returned after the attacks of September 11, 2001. -- "We have to ensure that Afghanistan successfully transitions into a period of stability and that past mistakes are not repeated," Aziz said. -- Kerry acknowledged those concerns and assured Pakistan that Washington valued its continued cooperation on fighting terrorism and on nuclear security. -- "We recognize that Pakistan is a vital partner in supporting a secure Afghanistan," he said. "And we know how closely Pakistan's own security is linked to Afghanistan's success." -- Despite such assurances, the strained relationship between the countries seeped through. Aziz said a prerequisite for a strategic partnership is mutual trust. -- "Once this trust is restored, then any unexpected incident or accident or disagreement on a policy or a tactic will not be able to derail the relationship," he said. -- Both sides welcomed a move toward warmer relations signified by the strategic dialogue and discussed increased investment in trade and energy. Kerry highlighted education and initiatives for the economic advancement of women in Pakistan.