When the season's first Everest expeditions arrived here this week, they were braced for all the physical and logistic challenges of the world's highest peak — from altitude sickness, to overcrowding on the summit.

This year, however, they face an unexpected political obstacle: a ban on access to Everest before May 10 to prevent pro-Tibet protests while China takes the Olympic torch to the 8,848m summit.

China announced last Monday that it was blocking expeditions to Everest from the Chinese side as well as to Cho Oyu, another peak over 8,000 metres, until after May 10.

As anti-Chinese riots flared in Tibet on Friday, Nepalese officials also declared that they were closing Everest from the south side at the request of Chinese authorities.

But climbers and agents are now warning the Nepal Government that it could endanger lives — and the country's multimillion-pound mountaineering industry — if it complies with China's request. Many are angry about what they see as the latest example of China's heavy-handed efforts to ensure co-operation against Tibetan activists from a tiny, impoverished neighbour.

“How could they do something so devastating to the economy and to a Nepalese icon?” said Peter Athans, a 50-year-old American mountaineer who has reached the summit of Everest seven times. “A country superior in size and power is grinding under foot Nepal's small but very important tourist industry.”

An expedition leader who has a group of 14 clients arriving next week said: “We just want to climb. But suddenly we have this other priority. We don't need the Chinese intimidating us.” The Nepalese Ministry of Tourism backed away from its ban yesterday, with a spokesman insisting that the season's 25 Everest expeditions would proceed as planned. “You can go any time to Everest,” he said.

But another ministry official told The Times: “We're planning new arrangements to stop crowds from arriving on Everest at the same time as the Olympic torch.” Agents said that the ministry was refusing to accept royalty payments of £5,000 per climber.

They said it had told them that expeditions could go no further than Gorak Shep, two hours' walk below Base Camp, between May 1 and May 10. They were also told that climbers would have to hand over mobile and satellite telephones to stop them speaking to the media from Everest.

The problem is that if climbers cannot reach Base Camp before May 10, by the time they have prepared the route and adjusted to the altitude, they will not reach the summit until mid-June. “That's when the monsoon comes any day and the ice gets more precarious,” Mr Athans said. “Essentially they'd be cancelling the entire season.”

That would be a huge blow to Nepal's economy as every climber pays between £17,000 and £35,000 plus royalties for an expedition, about 70 per cent of which is spent in Nepal.

Sherpas typically earn about £3,000 from a single two-month expedition and support their families on that for the rest of the year.

Agents have proposed a compromise whereby climbers would go as far as Camp Two to prepare their route, but would come down to Base Camp between May 1 and 10. They have also guaranteed that their clients will not stage protests. L. M. Poudel, the Tourism Secretary, was supposed to sign the compromise at a meeting yesterday, but he refused, saying that he did not have the authority.

That leaves several expeditions in limbo with at least two groups already in Kathmandu, and several more due in next week. “This is going to be a big disaster for this country,” said Jiban Ghimire, owner of Sherpa Shangri-La Treks and Expeditions.

He is expecting 14 American clients, who have all taken two months off work, on Tuesday. “They made this dream a long time ago,” he said. “If they have to cancel now, we're sending a terrible message to the world.”

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president