This new political momentum has not come about by happenstance. It is the result of a sustained effort both by Afghans and the international community to give this country a new lease on life.

After the tragedy of 9/11, indifference was no longer an option. Engagement was our only choice. Leaving Afghanistan to its own devices would have spelled more instability there, and more terrorist attacks worldwide.

There is no denying that the international community initially underestimated the magnitude of the challenge. After nine years of international engagement, it has become painfully obvious that the price we have to pay is much higher than expected, most of all in the loss of life of international and Afghan soldiers.

But Afghanistan is finally moving in the right direction. Maybe the insurgents think they can wait us out, but we will stay for as long as it takes to finish our job. Our training of Afghan soldiers and police is ahead of schedule, and by next year there will be a 300,000-strong Afghan security force — and it can’t be waited out.

By sending 40,000 additional international troops, we have demonstrated our commitment to protecting the Afghan people by holding areas we have liberated from the insurgents.

We are also finally taking the fight to the Taliban where it hurts them the most. Over the past months, the NATO-led International Security Assistance Force (I.S.A.F.) has launched military offensives into Taliban heartland — Helmand and Kandahar.

These operations, in which the Afghan security forces play an important role, will inevitably lead to intensified fighting. Regrettably there will be more casualties. But these military actions are of tremendous political importance. They contribute to the marginalization of the Taliban as a political and military force. And this will encourage many who joined the Taliban to quit their ranks and engage in the reconciliation effort.

Reconciliation, however, is no blank check. Renunciation of violence and respect for the Afghan Constitution, including women’s rights, is a precondition for successful reintegration. The Afghan authorities know this, and we will keep reminding them.

The next important political step after the Kabul conference will be the parliamentary elections in September. Despite death threats, Afghans have voted several times since the fall of the Taliban regime. Nothing could illustrate better the desire of the Afghan people to take their future into their own hands. NATO-led forces will support these elections, but the overall responsibility for their security and their free and fair conduct will lie with the Afghans themselves.

All these developments point in the same direction: a gradual transition to Afghan lead. This transition will not be done on the basis of an artificial timetable. It will be done on the basis of clear assessments of the political and security situation in each area. Where and when we do it, it will be irreversible.

Starting the transition does not mean that the struggle for Afghanistan’s future as a stable country in a volatile region will be over. Afghanistan will need the continued support of the international community, including NATO. It is important that we send a clear message of long-term commitment. The Afghan population needs to know that we will continue to stand by them as they chart their own course into the future.

To underline this commitment, I believe that NATO should develop a long-term cooperation agreement with the Afghan government.

We now have a new commander of the I.S.A.F. mission, Gen. David Petraeus. But our strategy hasn’t changed, because it is the right one. Our objective is clear: to ensure that Afghanistan does not again become a safe haven for terrorism.

We are building Afghans’ ability to resist terrorism and extremism on their own. We are changing the political conditions in the key strategic areas of Afghanistan; we are protecting the population; we are strengthening the capability of the elected government; and we are training the Afghan Army, to enable Afghanistan to look after its own security.

If we and our Afghan partners stick to our strategy and give it time to work, it will.