WASHINGTON - Former US Ambassador to Afghanistan Zalmay Khalilzad will join the State Department as an adviser on Afghanistan, US Secretary of State Mike Pompeo said on Tuesday as he headed to Pakistan to discuss Islamabad's role in helping to end the Afghan conflict."Ambassador Khalilzad is going to join the State Department team to assist us in the reconciliation effort, so he will come on and be the State Department's lead person for that purpose," Pompeo told US pool reporters traveling with him.Former cricket star Imran Khan's party won Pakistan's general election on July 25. The US military recently said it would cancel $300 million in aid to Pakistan over Islamabad's failure to take decisive action against militants.The Trump administration says Islamabad is granting safe haven to insurgents who are waging a 17-year-old war in neighboring Afghanistan, a charge Pakistan denies.US officials had held out the possibility that Pakistan could win back the aid if it changed its behavior.Pompeo said he would emphasize in meetings in Islamabad that Pakistan needed to help with ending the Afghan conflict, America's longest war.Experts on the conflict argue that militant safe havens in Pakistan have allowed Taliban-linked insurgents in Afghanistan a place to plot deadly strikes and regroup after offensives."We need Pakistan to seriously engage to help us get to the reconciliation we need in Afghanistan," said Pompeo. "The very reason for this trip is to try to articulate what it is our expectation is, the things that they can do, the things that they expect us to do, and see if we can't find a path forward together."President Donald Trump has expressed frustration at the lack of progress toward a US withdrawal from the Afghan conflict after 17 years. In a policy shift during a June ceasefire, Washington said it would "support, facilitate and participate" in any Kabul government-led peace talks with the Taliban.The surge in recent Taliban attacks has, however, raised questions about its interest in talks.Khalilzad's appointment signals that the administration is serious about an Afghan peace process. In addition to his experience advising or working for four US administrations and his knowledge of Afghanistan’s main languages, culture and politics, he is from the ethnic Pashtun majority.As an aide to President George W. Bush, he helped plan the US invasion of Afghanistan that followed the Sept. 11, 2001, attacks by al Qaeda, which had been based in that country. That invasion also ousted the Taliban, whose Islamist government ruled the country beginning in 1996.