SINCE the 9 /11 attacks, Pakistan has behaved toward US as both friend and adversary--and gotten away with it. The latest evidence of its duplicity is the revelation that Osama bin Laden lived for years in a house near Pakistan's national military academy and a local branch of its intelligence service without any evident interference. Even before the American raid last week on bin Laden's compound in Abbottabad, Pakistan had a huge credibility problem. It provides arms and safe haven for Afghan insurgent groups and pays their commanders to carry out attacks, but denies doing so. In the broader war on terrorism, Pakistan says it is completely on our side. In fact, its record is very uneven. It has been helpful in arresting some high-value Qaeda operatives and has allowed US to wage Predator drone attacks. But it has refused to move decisively against groups that Washington regards as terrorists and has put limits on American unilateral operations. It is not surprising, then, that no one took Pakistan's protestations of innocence after the discovery of bin Laden seriously. The killing of bin Laden only 60 miles from Islamabad, its capital, has put Pakistan on the defensive, and the nature of our strike capability is not lost on Pakistani leaders and their terrorist and insurgent clients. With American influence now at its peak and our troops still at full strength in Afghanistan, we have the leverage to force Pakistan to reconsider. US should pursue a two-stage strategy. First, we should formally present any information about Pakistani complicity in shielding bin Laden to Pakistan's leaders. Then we should follow up with demands that Pakistan break the backbone of al-Qaeda in Pakistan by moving against figures like bin Laden's deputy, Ayman al-Zawahri; remove limits on the Predator drone campaign; uproot insurgent sanctuaries and shut down factories that produce bombs for use against American and Afghan soldiers; and support a reasonable political settlement in Afghanistan. Such a settlement would ensure that Afghanistan does not become a haven for terrorists again, allay Pakistan's legitimate security concerns and provide amnesty-- and allow political participation-- for insurgents who lay down their arms and accept the Afghan constitution. In pursuing these goals, US should undertake a major diplomatic campaign, involving regional players like China and Saudi Arabia. If Pakistan fulfills these demands, US should reward it with long-term commitments of assistance, through trade benefits, programmes run by the World Bank and US Agency for International Development and similar efforts to promote development and education. But if Pakistan refuses to cooperate, US must put an end to its duplicity. First, US should reduce its dependence on supply lines running through Pakistan to Afghanistan. We should expand alternative supply routes through Azerbaijan and other countries in Central Asia. Also, as we draw down forces in Afghanistan, our logistical requirements will diminish; this will give US more leeway to consider unilateral attacks against terrorists and insurgents in Pakistan. Second, US should stay on the course set by Obama to build, train and support Afghan security forces and reduce our own military presence while retaining the capacity to provide air support, intelligence collection and other capabilities that the Afghans currently lack. Such a posture can strengthen Afghanistan against Pakistani interference and help persuade Pakistan to embrace a settlement. Third, US should conclude a longer- term agreement with Afghanistan to maintain a small, enduring military presence that would give us the capability to conduct counterterrorism operations and respond to possibilities--like Pakistani nuclear weapons falling into the hands-- of extremists. Fourth, US could consider seeking a UN Security Council resolution to authorise an investigation into how bin Laden managed to hide in plain view. The inquiry should examine the presence of al-Qaeda and other terrorist organisations in Pakistan. This strategy requires an improvement in the troubled relationship between US and Afghanistan. The impending arrivals of a new American ambassador, Ryan C. Crocker, and commander, Lt. Gen. John R. Allen of the Marine Corps, provide an opportunity to make progress. The challenge for the Afghan leadership and the new team is to achieve a partnership in which US sustains its commitment at much lower cost over time, while Afghanistan does its part by improving governance and the rule of law. It is in neither America's interest nor Pakistan's for relations to become more adversarial. But Pakistan's strategy of being both a friend and an adversary is no longer acceptable. While the killing of bin Laden was an important success, a greater achievement would be to transform US-Pak relations into a true partnership that fights terrorism, advances a reasonable Afghan settlement and helps stabilise the region. The writer is a counselor at the Center for Strategic and International Studies, was Ambassador to Afghanistan, Iraq and the United Nations during the George W. Bush administration.