UN aid agencies have said hundreds of thousands of people affected by the floods in Pakistan have yet to receive aid, adding that the relief operation remains underfunded.
Officials say the humanitarian situation there remains one of the most serious they have ever experienced.
Six million people are in need of immediate assistance, they add.
Extra emergency aid funds have been pledged to help more than 20 million people affected by the disaster.
The World Food Programme has so far distributed food to less than a million people. Of an estimated half-a-million families in need of shelter, just 98,000 had received tents, it said.
The obstacles are logistical - bridges have been washed away, roads blocked by landslides - and financial, reports the BBC's Imogen Foulkes in Geneva.
Thousands of homes and other buildings, including schools and hospitals, have been swept away, and crops for domestic food consumption and for export have been lost.
Pakistan's permanent representative to the UN Office at Geneva has appealed for more international attention and support for his country, describing the disaster as unprecedented.
"It is a catastrophe on a scale which is unparalleled as far as we can tell. Millions of people have been affected and the area covered is immense - it is about the size of England," Zamir Akram told the BBC.
One of the key questions is whether farmers will be able to plant their winter wheat crop in September, says the BBC's Mike Wooldridge in Islamabad.
Pakistan's High Commissioner to the UK said it could take five years and $15bn (£9.6bn) for the country to recover.
The floods began more than two weeks ago in the mountainous north-west and have swept south across a quarter of the country, including its agricultural heartland, leaving some 2,000 people dead.
In terms of new aid pledges, Australia has said it is offering an extra $21.6m, and Japan another $10m. Turkey has said it will double its donation to $10m in view of the worsening situation.
State media in Saudi Arabia said some $20m had been raised on the first day of a national campaign for the victims of the floods, while impoverished Afghanistan is offering $1m.
On Monday, the World Bank said it would loan $900m (£574m) to help the country recover from the floods.
But the UN's emergency relief operation remains underfunded, with just 36% of the requested $460m (£294m) received so far.
Aid agencies have said it has been difficult to communicate the scale of the disaster to the rest of the world.
"Remember that this flood has built up over time," Bill Berger, USAID's principal regional adviser for South Asia, told the BBC.
"I just don't think the world has realised the magnitude of this now, because this story has just been slowly increasing. It doesn't have the drama of an earthquake that impacts a huge number of people all at once."
Aid agencies have also blamed Pakistan's "image deficit" for the shortfall, as potential donors fear the funds would be diverted into extremism in the country.
A spokeswoman for Care International told the AFP news agency the UN had to do more to convince donors that the money was "not going to go to the hands of the Taliban".
"The victims are the mothers, the farmers, children. But in the past, information linked to Pakistan has always been linked to Taliban and terrorism," said Melanie Brooks.
Health officials have previously warned that disease could spread quickly among the millions of displaced people and that 3.5m children are at risk.
Aid agencies have warned that Pakistan would face "a second wave of deaths" from water-borne diseases and food shortages unless more aid arrived soon.
Meanwhile, rival political groups in Sindh province have been accusing each other of creating breaches in embankments and dykes to save their own towns and property.
Many of the breaches were reportedly made to divert flood waters away from military garrisons in the area.
Jacobabad city, for example, has been saved, but low-lying areas around it, including Dera Allahyar and some other towns in Balochistan province, have been inundated.
In India, Prime Minister Manmohan Singh has promised more funds to help areas affected by the recent devastating floods in Ladakh, a remote mountain region in Indian-administered Kashmir.
During a visit to the badly damaged town of Leh, he said all the destroyed homes would be rebuilt within the next two and a half months with money from a government relief fund.
The floods over 10 days ago killed more than 80 people and caused major damage to property. Many people are still missing.
BBC Urdu will transmit six daily bulletins in Urdu and Pashto providing vital information including how to stay safe, avoid disease and access aid. Special programmes will be broadcast each day in Urdu at 12.30, 15.30 and 18.30 and in Pashto at 12.45, 15.45 and 18.45 (local times).