At least 135 soldiers and civilians are buried by wall of snow at remote glacier base on border with India

A team of US soldiers has landed in Pakistan to help with an increasingly desperate search for survivors trapped under an avalanche in the north which engulfed 135 soldiers and civilians.

The eight-man, high-altitude search and rescue team comes at a time when the US and Pakistan are trying to rebuild relations after a long period of mutual acrimony and distrust.

Pakistan military sources confirmed the US rescuers flew into Islamabad from Afghanistan, where they are part of the Nato-led International Security Assistance Force (ISAF), soon after the US embassy announced it was prepared to give any assistance sought. They were due to fly early on Monday morning to the Siachen glacier, the world's highest combat zone, where hopes of finding anyone alive have started to fade.

Their arrival came almost 48 hours after a wall of snow and debris swept over the remote military base from where Pakistan guards its section of the desolate glacier against Indian forces.

No survivors or bodies have yet been recovered. The chances of survival for anyone trapped under the 25-metre high mass of snow and rock is thought to be extremely slight. The glacier in the heart of the Karakoram mountains and has been a flashpoint between India and Pakistan since the two fought over it in 1984.

Nazir Mohmand, a retired brigadier who served in the area, said the avalanche was "the worst in the history of Siachen" because it had consisted of boulders as well as snow. "Whatever the structure of a building, this avalanche was travelling at top speed and no building is likely to stand that," he said. Even if there were any trapped survivors, they were likely to be running out of oxygen, water and possibly succumbing to injuries.

Although the US has sent troops and helicopters from Afghanistan to assist Pakistan during previous natural disasters, relations between the two are currently poor, with particular sensitivity to the presence of US forces in Pakistan following last year's raid on Osama bin Laden's hide out.

"When an ally asks us for help, we are prepared to help," a US official said.

Yesterday, Gen Ashfaq Kayani, the chief of the army staff, personally oversaw rescue work at the Gayari sector of the glacier, which sits at an altitude of 4,572 metres. The army said more than 200 rescuers were digging into the snow, boulders, mud and slush using heavy machinery and sniffer dogs.Some heavy digging equipment was also airlifted into the area from the army's headquarters near Islamabad.

Permanently stationing troops in such an inhospitable area and keeping them supplied with even simple requirements such as food has been enormously expensive for both India and Pakistan.

The area has been quiet ever since a ceasefire was declared in 2003 and more troops, who often suffer from altitude sickness, have succumbed to the extreme climate than they have combat.

"Fighting on the roof of the world is extremely difficult, it takes effort just to survive," said Mohmand.