KATHMANDU (AFP) - The Everest climbing season will probably be called off this year following last week's avalanche that killed 16 sherpas, an organisation representing Nepalese expedition operators said on Friday.

Mountaineers and guides have been deserting the world's highest peak since the avalanche killed 13 sherpas and left three others missing and presumed dead on a treacherous ice field on April 18.

Mr Dambar Parajuli, president of the private Expedition Operators Association, said it appeared the lucrative climbing season was set to end soon amid a dispute between the Nepal government and sherpa guides over insurance and compensation.

"We can't officially say the season is closed this year, but chances are high," Mr Parajuli told AFP. "Several major expeditions have called off their plans, which means there won't be enough climbing sherpas to set the route up the mountain.

"In that case, others won't be able to climb either."

Sherpa guides, grief-stricken over the deaths of their colleagues, have threatened to boycott the climbing season, throwing mountaineers' plans into disarray and raising tensions.

Helicopter companies have struggled to cope with a flood of bookings from Everest base camp with the climbing season expected to be abandoned.

The accident - the deadliest in Everest's history - has shone a spotlight on dangers faced by sherpas who carve out climbing routes, fix ropes, repair ladders and carry gear up the mountain for their foreign clients.

Top mountaineering companies Himex, Altitude Junkies and Asian Trekking, were among the last to scrap their plans.

"Our expeditions have been cancelled," Tamding Sherpa of Himex told AFP.

"Sherpas are not in a position to climb, making it difficult to plan expeditions," said Dawa Sherpa, manager of Asian Trekking.

As helicopters buzzed overhead, American climber Robert Kay said he was preparing to leave base camp and abandon his third attempt to summit the 8,848m peak.

"Our company Altitude Junkies told us we are not going ahead this season, so we are just packing up now," Mr Kay told AFP.

Officials promised foreign mountaineers during talks held on Thursday that their climbing permits, costing at least US$11,000 (S$13,840) each, would be extended for five years in a bid to avoid messy refund claims for the lost season.

Under fire over its handling of the disaster, the government had been desperate to avoid a shutdown of the season that could lead to a huge revenue loss for the impoverished country.

Sherpas on Tuesday threatened to boycott the season after demanding that the government give higher compensation for the dead and injured, increase insurance payments and establish a welfare fund.

The government offered to set up a relief fund for injured guides using up to 5 per cent of fees paid by climbers, while raising life insurance payments by 50 per cent. Both amounts fall far short of the sherpas' demands.

The government, which has earned US$3.6 million this year from Everest climbing fees alone, had issued permits to 734 people this season.