Some of the helicopters flying aid to Pakistani earthquake victims could be grounded in a week by a cash crisis, United Nations officials have warned.
The UN says more than three million people lack food and shelter
The air aid and other relief measures will have to be scaled back unless donors send about $250m (£140m) immediately, officials say.
With winter looming, more than three million people in mountain villages lack food and shelter.
More than 55,000 people died in Pakistan in the 8 October earthquake.
Earlier Pakistani President Pervez Musharraf approved the release of more than $30m for the reconstruction of destroyed homes.
The money is to be divided between the two worst-affected areas, North-West Frontier Province and Pakistani-administered Kashmir.
But aid officials warned that more money was needed desperately to keep six UN helicopters operating, in a total relief fleet of around 60.
"We can keep the helicopters flying for one week," World Food Programme (WFP) emergency co-ordinator Michael Jones told a news conference in Islamabad.
"If we don't keep [them] running people will die," he added.
UN emergency co-ordinator Jan Vandemoortele told the same news conference: "Frankly, I don't know how to say this any more clearly in plain English. It's now or never. We will not have a second chance."
Pakistan's meteorological service has published its long range forecast for the coming winter and predicts worse weather than usual for the quake areas.
More snow and lower temperatures than usual are expected. Temperatures normally drop to minus 20C in the high mountains.
On Thursday, long-time rival India offered Pakistan $25m in aid, one of Delhi's largest donations to Pakistan in decades.
The pledge was part of $580m promised by donors following renewed UN warnings of an impending second catastrophe.
On Friday, a team of Indian officials left for Islamabad to hold talks on how to open the Line of Control - the de facto border in disputed Kashmir - to relief.
Correspondents say such a move would greatly aid relief.
Chairing the first meeting of the Earthquake Reconstruction and Rehabilitation Authority, President Musharraf expressed concern that some people in remote areas had not yet received any relief.
He promised tents within two weeks for those without shelter to save them from the severe cold.
But the UN has previously warned the world does not have sufficient supplies of the right kind of winter tents for the 800,000 people it estimates are without shelter.
A spokesman for the WFP said the agency had yet to reach half a million people in remote villages.
"More people could die in the aftermath from lack of shelter and food than in the earthquake itself," David Orr said.
Helicopters are flying dozens of sorties a day taking tents and food to those stranded, but the UN has said the scale of the disaster, given the type of terrain and the time of year, is worse than anything it has ever faced before.