United Nations Secretary-General Ban Ki Moon has urged the world to speed up aid to Pakistan after devastating floods which the government says have affected 20 million people.
Mr Ban is in Pakistan to visit Prime Minister Yusuf Raza Gilani and President Asif Ali Zardari, whose handling of the crisis has been widely criticised.
The floods, triggered by monsoons two weeks ago, have engulfed the Indus river basin, killing up to 1600 people.
The BBC reports that flood levels are expected to surge even higher along parts of the already dangerously swollen Indus river, with disaster officials saying "major peaks" were expected next week in Punjab and Sindh provinces.
The UN has so far appealed for $459 million in donations, but says billions will be needed in the long term.
Mr Ban described the destruction he witnessed as "heart-wrenching" and says the UN's agencies have provided assistance to hundreds of thousands of people, but six million still need food, shelter and water.
He announced the UN would give an extra $US10 million from its emergency fund, bringing the total it has pledged so far to $US27 million.
The head of the Red Cross in Pakistan, Pascal Cuttat, says much more is needed.
"We have to realise that the combined effort of all agencies and of the government of Pakistan at this stage will simply not be enough. This is a disaster of mind-blowing proportions."
Millions of children suffering - UN
The UN children's fund, UNICEF, says six million children are suffering from the floods - orphaned, lost and stricken with diarrhoea and heat exhaustion.
The fund is distributing high-energy biscuits to stave off malnutrition and diseases such as cholera and malaria, at relief camps in schools and in impromptu tent villages on the edges of towns and roadways.
The UN has confirmed at least one case of cholera in the Swat valley. Aid agencies are warning of a second wave of deaths from disease. About 36,000 cases of diarrhoea have been registered.
One third of the country affected
The UN estimates the floods now affect about one-third of Pakistan. Wheat, cotton and sugar crops are damaged.
The government is accused of being too slow to respond to the crisis.
Victims are relying mostly on the military and foreign agencies for help.
In an Independence Day speech, Prime Minister Raza Yusuf Gilani said Pakistan faces challenges similar to those during the partition of the subcontinent in 1947.
Partition led to the flight of at least 10 million refugees in the greatest migration in recorded history.
Mr Gilani and opposition leader Nawaz Sharif vowed on Saturday to work together to tackle the crisis.
President Zardari has drawn heavy criticism for going abroad to meet the leaders of Britain and France as the crisis unfolded and not shortening his trip.
