The United Nations and Red Cross increased their separate appeals for emergency funding over six months to more than half a billion dollars at a meeting with some 60 donor nations in Geneva.

UN Secretary General Kofi Annan told the meeting: "While no one today could have had the power to prevent the earthquake from happening, we do have the power to stop the next wave: the deaths and despair caused by freezing temperatures and disease, by lack of shelter, food and water."

Donors pledged an additional 525 million dollars (434 million euros) in assistance for Pakistan in reponse to the pleas, the United Nations chief chief emergency relief coordinator Jan Egeland said.

That comes on top of about 100 million dollars in pledges and cash.

But it was unclear how much of the new pledges would go towards the world body's emergency appeal, which was increased from 312 million dollars to 550 million dollars shortly before the meeting Wednesday.

Some of the pledges may be earmarked by governments for longer term reconstruction, or other assistance, UN officials emphasised.

Egeland also called for the promises to be turned into "actionable contributions" to allow relief agencies to deliver shelter and medical care to some 3.3 million homeless or injured survivors in Pakistani Kashmir.

Nonetheless, he acknowledged that the race to deliver help before winter takes hold next month had been energised.

"It is a deadline. This is a line of life or death for tens of thousands if not hundreds of thousands of people in the Himalayas," he told reporters.

"With the resources made available today and the commitments that will come in the coming days, we will redouble our collective efforts."

Officials warned that many relief agencies were running out of funding, hampering the delivery of crucial shelter equipment or food to the area before snow threatens to ground the relief effort next month.

Annan urged governments and even individuals to overcome their weariness with a succession of disasters this year and to match the unprecedented outpouring of generosity that followed the Indian Ocean tsunami.

"We need the support of governments, private citizens, the private sector and anyone who can spare a euro, a pound or a dollar," Annan told journalists.

The International Federation of Red Cross and Red Crescent Societies, which also took part in the meeting, doubled its separate appeal for 570,000 survivors in the worst-hit areas to 152 million Swiss francs (117 million dollars, 98 million euros).

The Red Cross warned in a statement Wednesday that thousands of the most vulnerable survivors in remote villages could die of exposure, nearly three weeks after the quake left 54,000 people dead and some 77,000 injured.

Some 700,000 people have received food but another 1.6 million are in need of sustenance, according to the UN.

About 120,000 tents have been delivered while 200,000 more are on their way for up to 3.3 million homeless.

One third of the injured quake victims who had received medical treatment had hands or arms amputated because they had been left with wounds for too long, Egeland revealed.

The UN has been struggling to collect funding for emergency assistance in Pakistan.

By contrast, the Red Cross appears to have generated a better response, receiving 42 million Swiss francs and pledges for a further 35 million, before it doubled its 73 million Swiss franc appeal Wednesday.

In Geneva, Pakistan's Senate chairman, Muhammad Soomro, and presidential advisor Salman Shah outlined the extent of destruction of life and property in Pakistan caused by the 7.6 magnitude earthquake.

"This is the time when the world has to come to our support," Soomro said.

Bad weather has been forecast in the region this week, while snowfall is expected to ground most of the 72 helicopters currently ferrying help to isolated villages in the region in about three weeks, according to the UN.