He may be dead, he may be trapped. But the fact is bin Laden has not been found

Osama Bin Laden has disappeared from the Afghan picture, the hounds have lost the scent, and without him for the first time since 11 September the American propaganda effort risks running out of steam.

Mr bin Laden endowed the "war on terrorism" with pin-sharp focus. In his absence, Afghanistan is suddenly once again merely a gun-saturated morass of feuding tribesmen; a treacherous, fiendishly complex political tangle. The man is badly missed.

There is a whiff of desperation in the air. Yesterday the US bombed a 12-vehicle convoy on the road in eastern Afghanistan, which a spokesman claimed contained al-Qa'ida leaders. America is preparing to use "thermobaric" bombs to suck the air out of Tora Bora's caves and tunnels, then to throw hundreds of ground troops in behind them to search for clues to where Mr bin Laden has gone. Some of the 2,000 US Marines in south Afghanistan are already interrogating al-Qa'ida fighters for information about their chief.

In Pakistan, meanwhile, where 1,500 US troops are stationed, a small number of American soldiers plus some CIA agents are helping the Pakistani military track down al-Qa'ida guerrillas who have fled across the border. Lt Cmdr Bruce Erikson, a spokesman at Central Command in Tampa, Florida, which is in charge of US military operations in the region, said, "It's safe to say we're actively involved in tracking al-Qa'ida in Pakistan." One reason for the growing direct US involvement in the manhunt is simmering dissatisfaction with the performance of their Afghan and Pakistani allies.

Mujahedin fighters, often brave to the point of total recklessness in combat, tend to be averse to the less heroic aspects of warfare, such as sifting through hundreds of tons of rock in the blasted caves of Tora Bora, even if there is the dim prospect of a huge reward for Mr bin Laden's capture at the end of it. The Afghans, it is said, are losing interest.

The problem in Pakistan is somewhat different. While the President, General Pervez Musharraf, has for the first time in Pakistan's history sent what an Islamabad official described as "tens of thousands" of troops into border areas to try and ensnare fleeing al- Qa'ida or Taliban fighters, there will be lingering doubts about the solidity of the Pakistani effort.

Julie Sirrs, a former analyst of Afghan and Pakistani affairs for the US Defence Intelligence Agency, said: "Like anything in Pakistan, the problem is that there isn't a united will ... Elements in the Pakistani military and the ISI [Inter-Services Intelligence Directorate, Pakistan's military intelligence agency] are very sympathetic to al-Qa'ida and will harbour and protect them."

But despite the obstacles, the search for Mr bin Laden must go on: American popular sentiment demands it, the desire for retribution for the atrocities of 11 September cries out for it, and the ratings will plummet unless the goal is pursued vigorously and publicly. General Richard Myers, chairman of the US joint chiefs of staff, said yesterday. "I don't know where [bin Laden] is. I'd rather not speculate if he is alive. We're following up all leads. If he has left Afghanistan, fine. In the end, I am confident we will find him."

So where to look? Until last week, the Pentagon seemed confident that he was holed up in a cave near Tora Bora. They had even named the place: Ghyreki Khiel mountain, six hours by donkey from Tora Bora; a complex of rooms dug into the hills, we were told, resembling an underground hotel.

All this certainty has gone out the window now that al-Qa'ida fighters – or most of them – have been either killed or flushed across the border. Now the jigsaw must be pieced together all over again. And despite the array of hi-tech equipment at America's disposal, including spy satellites, unmanned reconaissance planes and planes to eavesdrop on radio communications, the quest for Mr bin Laden is still a guessing game.

It is possible, for example, that he is already dead, either killed by his own hand or buried under tons of debris in a cave. It is one reason why the US commander, General Tommy Franks, is determined to explore the caves systematically using US forces, a complicated and dangerous task that could take months to complete.

But if Mr bin Laden has slipped away, the clever money is on him having vanished into the tribal areas just the other side of the high mountains that line the border. These tribal Pashtun communities customarily treat this border with contempt, and within tribal areas – such as Kurram, or North or South Waziristan – he will be among people who strongly supported the Taliban all along.

In these autonomous areas, the Pakistan army's writ has never run, even in times of crisis, and Mr bin Laden will again be the beneficiary of the extraordinary Pashtun hospitality that protected him in Afghanistan before the war. The drawback: these are villages where word of new arrivals spreads like lightning.

However warm the welcome, it is unlikely that the $25m terrorist will be able to rest easy in the North-West Frontier Province for long.

So he might head south along the border to seek refuge in the fiercely pro-Taliban Pashtun refugee communities in the Pakistani province of Baluchistan, between Quetta and Kandahar. Here again his welcome is likely to be warm, but again he is unlikely to be able to keep his presence a secret.

Once these obvious havens have been exhausted, the guesswork inevitably becomes wilder. One theory holds that he may already have crossed 200km of Pakistani mountains to reach Pakistan-occupied Kashmir, and the shelter of one of the training camps used by militants fighting in the Kashmiri jihad against India. Again, the welcome would be guaranteed – many of the jihadis there have trained in al-Qa'ida camps in Afghanistan, and increasing numbers of Afghan fighters have been sighted there as well. But there is none of the time-honoured tribal protection available in Kashmir, and with tension between India and Pakistan close to boiling point, his presence would become a serious embarrassment for Pakistan.

Another scenario sees him doing a flit through the sandy deserts of Pakistani Baluchistan, south of Kandahar, to the Arabian Sea, where he boards some salt-caked steamer bound for the Philippines or Morocco or one of half a dozen other possible destinations.

But if the complicated manoeuvres necessary to pull off such an escape are allowed, he might almost equally easily be imagined, minus beard and hair, with coloured contact lenses and Gap clothes, waiting on tables in Soho.