The people of Spain cannot be neutral spectators when faced with the consequences of an act of terrorism. It is not just a question of the sheer scale of the attacks perpetrated on September 11, nor the fact that they were particularly heinous.

Our own experience, the frequency and intensity with which we have experienced first-hand the death and destruction caused by terrorists, means that we too are the victims of this latest attack and that we share the grief of those who suffered directly.

Having recovered from the initial horror, we must now ask if anything has changed as a result of this demonstration of barbarity. Has the terrorist threat grown as a result of these attacks? Clearly not. What has happened is that the entire world has suddenly and dramatically become aware of a threat that has hung over us for a long time.

In this respect, we must be optimistic: the international community has reacted sensibly and responsibly to a threat that can no longer be ignored.

We in Spain have always wanted people to understand that all terrorists are the same. No misunderstood idealism, no conflict in need of a solution, no real or imaginary wrong can serve as a pretext to justify terrorism. To say the opposite - to give even the slightest justification for terrorism - is tantamount to turning the victims into the guilty.

Recourse to legitimate self-defence and the use of the most effective security measures are indispensable in order to combat terror. But above all it is essential to understand that terrorism, irrespective of the form it takes or where carried out in the world, seeks to destroy the values that lie at the very heart of our societies: individual freedom, parliamentary democracy and the rule of law.

Our system of values respects all ideas and beliefs. However, we cannot confuse this respect with conferring legitimacy on fanaticisms that prevent us from living together in a civilised manner. We are under an obligation to uphold the values that enable us to survive as free societies. And here there can be no backing down. The time has come for democracies to show their moral courage.

Never in the course of history has there been such an accumulation of power of all natures - political, military, economic, cultural, scientific and, above all, ethical - as that concentrated today in the countries that share the principles of a coexistence grounded on democracy, liberty and respect for human rights.

Never has humanity had at its disposal such an irresistible might with which to defend and uphold its belief in the dignity of human beings. This accumulation of power carries with it an equally large responsibility, one that until now has never been shouldered fully. We must all contribute to building a system of peace and security without divisions: a system that is today more feasible than at any time in the past.

The time has come to act with resolve and to reflect with serenity. We should harness this opportunity to lay the foundations of a stronger international order that accommodates cultural difference and respect for all beliefs. In other words, an order in which the rules are observed and defended, in which the common enemy, terrorism, will be forced to reckon with a will that until now has lain dormant to some extent. I do not need to underline the point that the main enemy of all terrorists is peace. Just cast our minds back to Yitzhak Rabin, the former Israeli prime minister, or Anwar Sadat of Egypt if proof were needed.

There is of course much that the international community can do. We must begin by punishing those responsible for such horrific attacks. We must also take other initiatives that we have not yet felt the need to implement. Recently, I said that terrorism was a crime against humanity. It is difficult to see it in any other light. Bringing to account terrorist organisations and their supporting networks requires new instruments and, above all, much more flexible and effective police and judicial co-operation. It is also necessary for the international community to target terrorism's source of funding. It is imperative, therefore, that countries work together to freeze any assets and investments held directly or indirectly by terrorist organisations. We must be firm with any state that harbours or affords refuge to terrorist groups.

There is much that we Europeans can and must do. The Council of Ministers of Justice and Home Affairs met yesterday. Today the Extraordinary European Council meets. I hope that enough specific and meaningful measures are adopted to enable us to tackle terrorism effectively. In view of our own situation, Spain has long advocated concrete action. Among other steps, I consider vital a European arrest warrant, measures to prevent the funding of terrorist groups and, lastly, sanctions against third countries that protect terrorist organisations.

I fully understand that difficulties of various kinds have, until now, prevented us from taking concerted action among all countries to combat terrorism. Some of these are ideological difficulties, others stem from our respective legal traditions. Still, the enemies of our values and of peace should not continue to be given the upper hand. Let us not delude ourselves: anyone who believes that peace can be bought by shying away from the problems is totally mistaken.

On September 11 we saw just how far terrorists are capable of going. We saw the extent to which they can seize upon any opportunity, however slight, that we leave open to them. If we do not act, rest assured they certainly will act again.

The writer is prime minister of Spain