The UN says the shortfall in aid for victims of the South Asian quake has made the relief situation worse than after last December's tsunami.
An operation like the 1940s Berlin airlift is needed, the UN says
UN emergency relief chief, Jan Egeland, said the organisation had never seen such a "logistical nightmare".
Nato began flying in 900 tonnes of aid on Thursday, but Mr Egeland said a massive airlift was also needed to bring people out of remote areas.
Pakistan says nearly 50,000 people died in areas under its control.
Local officials put casualties far higher, and the number is expected to rise. At least 1,400 others died in Indian-administered Kashmir, officials say.
Mr Egeland said an airlift was needed of the proportions of the Berlin blockade of the 1940s, when Allies flew in supplies to the divided city in communist eastern Europe.
He said aid had to be sent in, and tens of thousands of homeless and injured people flown out, of remote regions before winter set in.
Mr Egeland said of the aid sent so far: "This is not enough. We have never had this kind of logistical nightmare ever. We thought the tsunami was the worst we could get. This is worse."
The tsunami, which struck on 26 December, killed more than 200,000 people around the Indian Ocean.
Mr Egeland, speaking in Geneva, said the quake situation was becoming worse by the day.
"Tens of thousands of people's lives are at stake and they could die if we don't get to them in time."
Nato on Thursday began an airlift of 900 tonnes of aid from warehouses in Turkey.
Ten thousand tents will be flown to Pakistan over the next few weeks, although the UN has warned there may not be enough winterised tents in the world to meet the needs of the earthquake victims.
The UK announced another $35m (£20m) towards the relief effort.
'Second wave of death'
Mr Egeland said only $86m had been pledged of the $312m the UN had asked for to fund the relief operation - and far less actually received in hard cash.
Heavy duty tent designed for long-term use by a single family
PVC groundsheet sewn onto the sides for wind proofing and to retain warmth
Some types are designed to accommodate cooking stoves
ICRC estimates that 30,000 such tents are required in Pakistan
Earlier, UN Secretary General Kofi Annan called for the global relief effort to be increased to help three million people made homeless by the 8 October quake and facing the fierce Himalayan winter without shelter.
"That means a second, massive wave of death will happen if we do not step up our efforts now," he said.
Mr Annan said that in the most affected areas hospitals, schools, water systems and roads had all been destroyed.
He called upon top international representatives to attend a UN-sponsored donors conference in Geneva, Switzerland, next week.
Mr Annan's chief aid co-ordinator in Islamabad, Andrew MacLeod, told the BBC: "If the second wave of deaths hit, it's the major donors that are going to have to look at themselves in the mirror and ask why."
On Thursday the Global Green Peace group warned of another danger for quake survivors - the possible shifting of thousands of landmines along the Line of Control in Kashmir.
However, both Indian and Pakistani military officials said if there was any shifting, civilian areas would not be affected. Similar fears in Sri Lanka after the tsunami proved to be unfounded.
Doctors have also warned that tetanus could become a big problem in quake areas if vaccinations are not carried out properly.
WHO doctor, Irfan Noor, said 18 cases had now been reported from the Balakot area of Pakistan's North-West Frontier Province and that many of those affected were children.
He said there had been three deaths so far from tetanus, two of them children.
The BBC's Imogen Foulkes in Geneva says the earthquake has come at a time when aid agencies are already very stretched carrying out relief work in storm-hit central America, as well as Niger and Sudan.
She quotes a senior official as saying agencies would find it very difficult to respond to another disaster.
While 92 countries had helped nations hit by last year's tsunami, only some 15 to 20 countries had responded to the quake, the Reuters news agency quoted Mr Egeland as saying.