As you head out of bustling Peshawar in north-west Pakistan towards the Khyber Pass and the Afghanistan border, you drive along a street with shops selling lethal goods. Here you can order a copy of practically any handgun or rifle for prices starting from as little as £10.

There is no bigger contrast to the ugliness of the deadly arms that are so easily available in this region to the breathtaking beauty of the Khyber Pass.

The Khyber Pass has been an important trade route between Pakistan and Afghanistan for centuries, with goods and arms making their way over its rugged roads.

This week the road between the Afghan capital, Kabul, and Peshawar was thronged with cargo of a different kind; thousands of tired and hungry refugees fleeing their homeland for fear of an attack by the US.

Homes in Kabul emptied as weary men, women and children, already battered by more than two decades of war and civil strife, made their way on foot, on horseback, or by truck towards the Khyber Pass and safety. By the end of the week it was estimated half of the city's population had gone.

The fleeing throng are the first victims of "the first war of the 21st century", before a single shot has even been fired.

The very sight of the Khyber reminds one of the conquerors who forced their way through its dangerous mountainous terrain when launching invasions. It was first used as a strategic gateway in 326 BC, when Alexander the Great and his army marched through to reach the plains of India.

There is no doubt the rough territory will be unwelcoming for any military force that may be get involved in the regions anticipated conflict. The mountains on either side can be climbed only in a few places. The pass is walled by precipitous cliffs.

The Pashtuns are the ethnic group which makes up most of the population of Afghanistan and Pakistan's north-western frontier.

They comprise almost 100 tribes, each occupying a particular territory. They have a long history of bloody inter-clan disputes. Any US forces in Pakistan will have to deal with the tribes.

Unlike the Gulf War, when the US was able to use friendly Saudi Arabia to launch attacks against Iraq, Pakistan and its people won't be going out of their way to help.

Already, the resentment of the US is clear. A group of journalists received permission to drive across the Khyber Pass this week to the border crossing-point at Torkham to see what the refugee situation was. Each car had a solider armed with a Kalashnikov rifle as an escort, something the Pakistan authorities insisted upon for our own safety.

Our mere presence in Torkham was enough to upset rifle-wielding Taliban soldiers, and we beat a hasty retreat. Driving back to Peshawar from Torkham, we stopped our car to take pictures across the valley. Two armed soldiers, members of the Afridi tribe, appeared. They did not want pictures taken of their territory and they asked us to leave.

Across Pakistan this week, people were resigned to the inevitable attack by America. In the capital, Islamabad, it was business as usual on the surface, but underneath the veneer of normality, there were signs that the country was bracing itself for a strike on its neighbour. The military presence on the streets increased significantly. Most of the expatriate staff and dependants of foreign diplomats began to leave. British Petroleum was the first of several oil companies in the city to order its expat staff home.

Islamabad is one of the youngest cities in the world, built only 30 years ago. It is not like your typical Asian capital. Built on a grid system, it is divided into eight units, named after the first eight letters of the alphabet. The streets are wide and it is orderly. Each unit has its own bazaar and centre.

In the Karachi Company bazaar in unit E, you will find it hard not to meet an Afghan. Most of the people here have fled from Afghanistan at some stage in the last 23 years, either from the 10-year war with Russia or from the internal tribal conflicts which have been a feature of life since.

Support for Osama bin Laden is unequivocal. Traders are horrified at the prospect of a US attack on their homeland.

Naveed Daniwa arrived here at the end of the Russian war. He still has a brother and sister in Kabul. He has made a good life for himself in Islamabad and has several clothing stalls in this thriving market area.

He is concerned for the safety of his family back in Kabul, who had decided not to leave the country. He would be happier if they left before a US attack. "America is a bully. There is no evidence against bin Laden and they have no business attacking our country. They are intent on eliminating the Muslim people and this is their excuse," Naveed said.

In the market square, about 100 men are silent in prayer. Perfectly co-ordinated, they go on their knees and bow to Allah. All wearing white caps, they lift their heads at the very same time, oblivious to the bustle around them.

"We are Muslims, but George Bush has branded all of us terrorists. If there is evidence against bin Laden, so be it, but in the meanwhile, he has no business coming near us."

Another sign of the escalating crisis was the invasion of journalists from all over the world. The Marriott Hotel was turned into an unofficial media centre, with the Pakistan Foreign Ministry holding its press conferences there every day. The rooftop was transformed into an open-air television studio. Networks including CNN and BBC World news have permanent perches, broadcasting live around the clock.

The rumour machine was rife. The arrival of CNN's chief international correspondent, Christine Amanpour, sparked huge speculation. She was first to break the news of the attack on Iraq, which marked the start of the Gulf War in 1990 in a live telecast from the top of a Baghdad Hotel.

The fact her husband is Jamie Rubin, a former spokesman of Madeleine Albright, convinced people she was working on inside information.

There was a sudden brief power cut in the hotel on Wednesday night. Correspondents rushed out of their rooms swapping all sorts of wild theories about the cause of the blackout.

Being a Muslim country, alcohol in the hotel was restricted. You could only order in your room. The drink, wrapped in a black plastic bag, was brought by a porter. Before he handed it over, a passport had to be shown and a lengthy form filled out.

The Afghan Embassy in Islamabad was busy dealing with journalists looking for visas to allow them to go to Kabul. It turned out to be a useless exercise. The last foreign journalist remaining in the Afghan capital, CNN's Nic Roberstown, was asked to leave on Thursday.

Applying for a visa was an intimidating experience. The armed guard outside the embassy scowled as he ushered me in. The official in the visa office threw the application form at my feet, smirked and walked away.

In contrast to the modern, sterile Islamabad, the frontier city of Peshawar is crammed with people jostling for space on the choking streets. It is full of colourful markets, the Khyber bazaar, the bird bazaar, the basket bazaar.

Bin Laden is a local hero. He is so popular that some shops were looking forward to a mini bonanza. Thousands of posters and T-shirts with his picture were produced after US officials began blaming him for last week's attacks on the World Trade Centre and the Pentagon.

One of the shirts read "World Hero Osama bin Laden" and "The Great Mujahid (holy warrior) of Islam".

However, their windfall was brought to a swift end when the authorities issued an order to stop the sale of bin Laden merchanise as pressure increased on the Pakistanis from the US to assist in action against Afghanistan.

Outside Peshawar, the human fallout from the crisis was unfolding. Refugees lucky enough to get over the border at Torkham started to trickle into the already overcrowded refugee camps. Conditions there were appalling, with aid agencies reporting disease and deaths.

The north-west Frontier Province announced it was going to build 25 temporary refugee shelters to help cope with the one million refugees expected over the border.

The UNHCR put an emergency plan in action and predicted a huge human tragedy if the US attacked Afghanistan. The World Food Programme warned of pre-famine conditions in Afghanistan, and said there were only food supplies to last the next two to three weeks.

Pakistan's President, Gen Pervez Musharraf, was trying play a delicate balancing act. Pakistan is only one of three countries to recognise Afghanistan.

He was trying to keep the US and the international community happy by co-operating with the fight against international terrorism, while at the same time keeping the extreme Islamic groups at home on side. As Islamic groups in the country made their views louder, he addressed the nation on Wednesday night, warning that a wrong decision could cause serious harm.

A meeting of Muslim clerics in Kabul offered the slimmest of hopes that the Taliban elders would hand over bin Laden. The elders tried a compromise, saying that bin Laden should leave voluntarily in his own time. That was not enough for the US.

"That is it. That was the last hope. It is inevitable now," a moderate Muslim businessman said.

Anti-American protests and rallies started to increase, culminating in the nationwide strike yesterday. Foreign journalists were warned in a letter from the Government Information Office not to wander freely in the markets. We were told to carry our passport with us at all times and not to roam in the tribal areas outside the city without valid permits.

It has been a week of waiting for the US retribution. So far, people's worst fears have not been realised, but it appears to be a case of not if, but when, the revenge is sought.