A week ago, Nepal's tourism minister, Prithvi Subba Gurung, announced that no climbers would be allowed beyond Mount Everest base camp on the Nepalese side until after May 10. The move came amid widespread speculation that Beijing had requested the ban be imposed to allow China's Olympic torch relay on the Tibetan side of the mountain to proceed without the threat of protests.

Mr Gurung said the restriction would 'prevent some people who would infiltrate and cause trouble during the time they take the torch to the top'.

The window of opportunity for attempts on Everest is limited because monsoons set in by early June, melting ice flows and making it virtually impossible to get to the summit. By banning climbers from going beyond base camp before the Olympic torch relay is over, expedition teams have no time to acclimatise their members for attempts on the 8,848-metre summit by climbing up to the higher camps and back down again before going for the summit.

The decision has already scuppered dozens of expeditions, including an attempt by prominent 64-year-old British explorer Sir Ranulph Fiennes, who planned to set out from Kathmandu next month and reach the summit with his Himalayan guide on May 15.

Sir Ranulph's summit bid would have raised more than US$4 million for a cancer charity. Businessman Paul Sykes, who helped fund the expedition, told his local newspaper, the Yorkshire Post: 'Banning all climbing on Everest is not the action of a government that is fit to host the Olympic Games.'

The controversy has also reverberated in New Zealand, where the first man to conquer Everest, Sir Edmund Hillary, died this year. Expedition leader Guy Cotter said the ban was 'like Australia telling New Zealand not to hold the Rugby World Cup because it involved political issues'.

But the greatest impact of the ban is being felt in Nepal itself, where the business of tour companies and the livelihoods of hundreds of Sherpas are in jeopardy this summer. 'There was no warning at all - just the announcement last Friday,' said Mr Gael, who runs the Adventure Silk Road tour company.

'I phoned the ministry directly when we heard the news and I was simply told the decision was taken because of a 'mutual understanding' between Nepal and China.

'Our problem is that we are sandwiched between India and China and dependent on them. So when issues like this arise, we have to consider their needs, even if it does great damage to us in Nepal.'

The issue has brought resentment of Nepal's giant northern neighbour bubbling to the surface, along with frustration at the government's inability to stand up to Beijing when it is asked to act against its own national interests.

One Kathmandu tour company owner, who asked not to be named, said: 'This decision is crazy. It is kowtowing completely to the Chinese and Nepal will get absolutely nothing in return. We never do.

'The Nepalese government should never have agreed to this ban. What do they think climbers are going to do? Climb to the summit and then run down the other side to disrupt the torch relay? How can anything that happens on the Nepalese side possibly affect the relay in any way?'

China's request to Nepal to ban expeditions appears to pre-date the current unrest in Tibet, which exploded into violent confrontations eight days ago - the day Nepal announced its ban on all Everest expeditions before May 10.

Expeditions on the Chinese side of Everest have already been banned and security around Everest base camp in Tibet has been high since last April, when US protesters videoed themselves unfurling 'free Tibet' banners there.

The recent unrest in Tibet has also hit Nepal's tourism industry, as travellers with itineraries to visit first Kathmandu and then Lhasa have had their permits to cross the border into China cancelled. 'Many of them have pre-paid air tickets and hotel bookings but Chinese airlines and hotels hold on to the deposits and charge cancellation fees, even though it is their government that has cancelled the permits and shut out visitors,' Mr Gael said. 'We usually end up having to pay those fees and deposits ourselves.'

Nepal's government has been stung by international criticism of its decision to ban Everest expeditions and has suggested in recent days that the situation may affect the outcome of next month's elections.

Many overseas expedition groups have refused to abandon hope for journeys that had been years in the planning before a single day's announcement put them on hold.

Because China's own timetable for the torch relay is flexible and may take place in late April rather than early May, some expeditions are continuing preparations in the hope the ban will be lifted in time for them to race to the summit.

It is exactly this kind of optimism that could turn an expensive diplomatic incident into a human tragedy, warns veteran Russian climber and tour leader Alex Abramov, who has already taken the decision to postpone his expedition this year.

'Maybe it is possible to get some acclimatisation on smaller peaks and then climb Everest in three weeks. But if you climb a great mountain, you shouldn't be exposed to shame and humiliation at the start of the expedition,' he writes on EverestNews.com. 'It is possible to make the summit 'at any price' - but in these situations, leaders and team members have a greater chance of making mistakes and getting into serious trouble.'