Fearing an imminent dirty bomb attack, scores of nuclear scientists with sophisticated radiation detection equipment hidden in briefcases and golf bags scoured five US cities over Christmas and New Year, officials involved in the emergency effort say.

The call-up of radiation experts to Washington, New York, Las Vegas, Los Angeles and Baltimore - the first since the weeks after the World Trade Centre attacks - was conducted in secrecy, in contrast to the very public cancellation of flights from Europe and Mexico.

The terrorism crisis began late on December 19, when analysts assembled what they described as extremely specific intelligence, including electronic intercepts of phone calls and emails from al-Qaeda operatives, of an attack on US soil. A "code orange", or high alert, was issued on December 21.

Even now, hundreds of nuclear and bio-weapons scientists remain on high alert at several military bases across the US, ready to fly to any trouble spot. Pharmaceutical stockpiles to treat victims of biological attacks were loaded on transportable trucks at key US military bases.

Officials said one of their main challenges was determining whether al-Qaeda is planting provocative but false clues as a diversion or as deliberate disinformation to test the US response.

The attention to a potential dirty bomb attack resulted not from specific information pointing to an attack, but from the belief among US officials that al-Qaeda was sparing no effort to try to detonate one.

A dirty bomb attack, in which a conventional bomb is detonated and spews radioactive material and radiation across a small area, is unlikely to cause mass casualties, but could cause panic and devastate a local economy.

US officials became concerned that a large, open-air New Year's Eve celebration might be a target. While the perimeters of football stadiums can generally be secured, outdoor celebrations are much more vulnerable.

There were fears al-Qaeda operatives would hijack and crash an overseas flight into a US city or the ocean. Another was that terrorists would shoot down an aircraft with a shoulder-fired missile.

On the same day the national threat level was raised to orange, the Homeland Security Department sent out radiation detectors and hundreds of pager-sized radiation monitors for use by police in the biggest US cities.

It also dispatched the Energy Department radiation experts to cities planning large public events. In Manhattan, up to a million people were expected in Times Square on New Year's Eve.

The Energy Department scientists arrived to take covert readings on their disguised radiological equipment in a variety of settings. "Our guys can fit in a sports stadium, a construction site or on Fifth Avenue," one Energy Department official said. "Their equipment is configured to look like anybody else's luggage or briefcase."

Starting on December 22, the teams criss-crossed US cities, taking measurements 24 hours a day.

On December 29 in Las Vegas, the searchers got their first and only radiation "spike" - at a self-storage warehouse. The White House was notified.

It turned out that the locker belonged to a homeless man and, tucked inside his duffel bag was a cigar-sized radium pellet, used to treat uterine cancer. He had found it three years before. The man was released. Five tense hours after their radiation detectors had spiked, the storage locker security crisis was over.

After the surprise attack on September 11, 2001 the resolve of the US Government never to be caught unprepared again by a terror attack is entirely understandable. There is ample intelligence that al-Qa'ida is ready to mount new attacks on US cities and power plants using civilian airliners as flying bombs and the US Government has no option but to be ready if and when they come. This will likely ensure air travellers will suffer similar inconveniences to those of recent days - flights cancelled or diverted in mid flight - for years to come. It explains why the Americans are insisting sky marshals ride shotgun on international flights into the US. It accounts for the upgraded identification people entering America will require. And it makes sense of the demand that flight crews check airline toilets for suspicious packages, with an FBI report revealing terrorist plans to smuggle bomb components on board jets for in-flight assembly.

None of these measures are popular - they will make entering the US a harder and more inconvenient process. A judge in Brazil has directed that US visitors must be finger-printed, in retaliation for the American requirement for Brazilians arriving in the US. Portugal, Denmark and Sweden have refused to put sky marshals on flights to the US. But foreign complaints are not likely to sway the Americans.

For the American people, September 11 was a rerun of Pearl Harbour - an act of war. And in wartime national security takes priority. This does not mean American security standards are all beyond debate. Warnings that passengers should not queue in aircraft aisles for toilets looks foolish. The prospect of a fire-fight between sky marshals and a terrorist on a packed jumbo jet is a grim one. And travellers mistaken for terrorists arriving in the US can expect a hard time. But the memory of the twin towers burning will not quickly fade from the American mind. We might not like it, but a more suspicious welcome for travellers to the US is here to stay.

January 07, 2004
When most people think about US foreign policy, they think about the war on terrorism: the reconstruction of Iraq and Afghanistan, the troubles of the Middle East and lurking terrorist cells.

This preoccupation is natural. International terrorism literally hit home on September 11, 2001, and, for understandable reasons, an outraged American public wants those responsible brought to justice – and a foreign policy that makes sure such events never happen again.

The war on terrorism will remain the US's foreign policy priority for as long as necessary, because terrorism – potentially linked to the proliferation of weapons of mass destruction – now represents the greatest threat to American lives.

But that does not mean that terrorism is the only issue we care about.

George W. Bush has a vision of a better world and a strategy for translating that vision into reality. First laid out publicly in September 2002, in the National Security Strategy of the United States, that strategy is broad and deep, far-ranging and forward-looking, attuned as much to the opportunities as to the dangers that we and others face.

US strategy is widely accused of being unilateralist by design. It is not. It is often accused of being weighted in favour of military methods. It is not.

It is frequently described as being obsessed with terrorism and hence being biased towards pre-emptive war on a global scale. It most certainly is not.

The President's strategy is one of partnerships that strongly affirm the vital role of NATO and other US alliances – including the UN. Beyond partnership comes principle. The President's strategy is rooted in the promotion of freedom and dignity worldwide. Free trade and new initiatives for economic development also figure prominently in the President's strategy, as does playing a role in helping to solve regional conflicts such as that between Israelis and Palestinians.

Another priority is developing co-operation among the world's major powers. It is here that the key to a successful conclusion to the war against terrorism lies.

We do not see the war against terrorism and the nurturing of such constructive relationships as mutually exclusive. We conduct the war on terrorism with an eye towards major power co-operation, and we seek enhanced major power co-operation with an eye towards success in the war on terrorism. The logic of this dual approach rests on the fact that terrorism threatens the world order itself – and thus creates a common interest among all nations that value peace, prosperity and the rule of law.

As Bush has written: "Today, the world's great powers find ourselves on the same side." This development is not just good news; it is revolutionary. For too many centuries the imperial habits of countries squandered untold resources and talent by jousting for land, glory and gold.

The futility of such habits has become evident in the 21st century. The possession of vast territory, raw natural resources and brute power guarantees neither prosperity nor peace. Investment in human capital, social trust, trade and co-operation within and among nations does.

The sources of strength and security for one nation thus need no longer threaten the security of others. An insight of the American founders – that politics does not always have to be a zero-sum competition – has at last been adopted by enough people worldwide to promise a difference in the character of international relations. If, instead of wasting lives and treasure by opposing each other, today's major countries pull in the same direction to solve problems common to all, we will begin to redeem history from much human folly.

We must not take the present peace among the world's nations for granted, for differing interests may still lead nations to clash. We have to work at it with patience, mindful that major war has broken out in the past despite a widespread conviction that it simply could not happen again.

Of course, we want to promote human dignity and democracy in the world, to help people to raise themselves from poverty and to transform the inadequate system of global public health. We are pursuing these goals.

But only if the deep peace of our era can be "preserved, defended and expanded" – to use the President's words – can we pursue these goals for as long as it will take to achieve them.

And make no mistake, these are the central goals of American policy. We fight terrorism because we must but we seek a better world because we can – because it is our desire, and our destiny, to do so. This is why we commit ourselves to democracy, development, global public health and human rights, as well as to the prerequisite of a solid structure for global peace.

These are not high-sounding decorations for our interests. They are our interests, the purposes our power serves.

Today, the US's motives are impugned in some lands. But as we preserve, defend and expand the peace that free peoples won in the 20th century, we will see the US vindicated in the eyes of the world in the 21st.

It would be churlish to claim that the Bush administration's foreign policy has been error-free from the start.

But we have always pursued the enlightened self-interest of the American people, and in our purposes and our principles there are no mistakes.

Our enlightened self-interest puts us at odds with terrorists, tyrants and others who wish us ill.

From them we seek no advice or comity, and to them we will give no quarter. But our enlightened self-interest makes us partners with all those who cherish freedom, human dignity and peace.

We know the side on which the human spirit abides, and we take encouragement from this as our strategy unfolds. In the end it is the only encouragement we really need.

Colin Powell is US Secretary of State.