A year after the Bonn Conference on Afghanistan's future, there is considerable ground for optimism about that country. Living conditions are still harsh for many people, and episodic violence continues. But at the same time substantial progress has been made in Afghanistan, thanks to patient, persistent efforts both inside and outside the country.

With leadership from the United States, al Qaeda forces and the Taliban were defeated, relief was provided for the population and some 2 million returning refugees, and a start was made on developing sustainable Afghan self-governance. Barring a reversal by either the Afghans or their international supporters, the stage is set for much greater progress over the next year, although serious problems will remain. But if U.S. leadership falters, so will other international efforts, with potentially disastrous consequences not only for the Afghan government, but also for the campaign against al Qaeda and the future of neighboring Pakistan.

The United States had a wise initial strategy for avoiding the sort of fatal mistakes the Soviets made in Afghanistan in the 1980s. By establishing a broad political coalition, including Muslim countries, and using small Special Forces teams to fight alongside Afghans against al Qaeda and hard-core Taliban, the United States avoided being seen as occupying Afghanistan or going to war against Islam. This was reinforced by large-scale relief for the destitute population and the political empowerment of Afghans by the Bonn Conference and the country's loya jirga, or national assembly. The United States, Saudi Arabia, Japan and the European Union set up the Afghan Reconstruction Steering Group, which includes the World Bank and the Asian Development Bank and is becoming increasingly effective. The United States, France and Britain have begun a multi-year program to train a new Afghan national army. Germany has done the same for the police, with U.S. help. The threat from al Qaeda and the Taliban has been reduced to manageable levels in much of the country, and the International Security Assistance Force has helped establish the security that is vital for Kabul. The U.N. Assistance Mission for Afghanistan and Special Representative Lakhdar Brahimi have won the confidence of all parties with low-key advice and coordination for donors and the new government.

Starting from zero a year ago, the administration of President Hamid Karzai has achieved many attributes of a responsible government. It has a long-term national development framework and budget, worked out with the World Bank, the United Nations, the United States and other donors, and is carefully applying it to ensure that donor proposals meet Afghan realities. A central bank, fiscal discipline and a new national currency have been established. Construction of the large-scale Ring Road program has begun; large-scale community development projects will soon follow smaller efforts. An Afghan Defense Commission (including senior "warlords") has reached agreement on the size, makeup and training of the new army and the demobilization of local militias. This will take time but will ultimately be the Afghans' own solution to their endemic security problems. Prudence has proven to be better than prematurely deploying unready international peacekeepers (with inadequate resources) to remote areas. The violence that would have followed such deployments, involving al Qaeda, the Taliban and warlords, would have seriously disrupted both the war against terrorism and the process of gradually stabilizing the country.

As it stands today, the process of building the new government at the center appears to have readied it for the next decisive step: becoming effectively operational in the countryside.

For this to succeed, the flow of international assistance, which has recently accelerated, must continue. This includes the Bush administration and Congress actually funding the four-year, $3.3 billion Afghanistan Freedom Support Act, as well as training the country's army -- actions vital both for the badly needed resources and for the strong signal to all parties of a long-term U.S. commitment. It will also require that international donors and nongovernmental organizations reorient their programs outside of Kabul in order to enhance the operations of the government ministries rather than the prestige of donors and regional power centers.

Obviously, all this cannot happen without security. The United States and President Karzai have agreed on a new plan to shift the priority of coalition efforts from combat to stability operations for most of Afghanistan during the next year, creating eight or more joint regional teams with civil and military membership, including coalition forces and small Afghan army contingents. These teams will have enough capability -- with on-call backup -- to provide increased security for reconstruction by the Afghan government and international donors.

The achievements of the first year augur well for the long-term future of Afghanistan. But should the United States falter in its leading role, so would the coalition. This would create dissension within the Afghan government and with the provinces, reigniting ethnic and regional rifts. Worse, it would reinvigorate al Qaeda and the Taliban, which could shift back from Pakistan for a major assault in Afghanistan. Backing away would also have a devastating effect on efforts by Pakistan's President Pervez Musharraf to uproot al Qaeda and the Taliban, neutralize their supporters and bring political, economic and social reform to that country. And it could have serious negative repercussions on Kashmir and India-Pakistan relations. Given the potential that still exists for a political-religious explosion in Pakistan, with its nuclear weapons, and the prospect for increased tensions stemming from Iraq, this could have incalculable consequences for the entire region and the United States.

The writer is a former ambassador to Pakistan and a visiting fellow at the National Defense University.