Amid growing recrimination over the slow international response to the Pakistan flood crisis, the US has increased its aid to the country to $150m (£96.2m).
The announcement came after the European Union increased its pledge of emergency help to $135m and Saudi Arabia promised $105m.
The Obama administration has already deployed army helicopters to hard-hit areas as part of a package worth approximately $90m. Senator John Kerry, a leading Democrat who is visiting Pakistan to see the flood damage, said that would increase to $150m. The revised figure is expected to be announced at an emergency session of the UN in New York today.
The Pakistan government has been criticised for its ineffectual response to the disaster, but donor countries have until now been similarly slow to pledge relief funds.
Islamist organisations – some with alleged links to extremist groups – have been active in the flood-hit areas. There are also concerns that the lack of resources could stoke social unrest and lead to political instability.
"We don't want additional jihadists [and] extremists coming out of a crisis," Kerry told reporters after meeting US military personnel taking part in air relief missions.
The Asian Development Bank said it would redirect $2bn of existing and planned loans for reconstruction.
"If we don't do it quick, if we don't do it well, what will the Pakistani people think?" said Juan Miranda, the bank's director general for central and west Asia. "We have to put every road and every bridge back into the shape where they should be."
The announcement of more EU money followed criticism of Brussels' aid effort from France and Britain. The French president, Nicolas Sarkozy, this week accused Brussels of being slow to react to the crisis and called for a new European rapid reaction force for coping with international natural disasters.
Saudi Arabia yesterday announced a $105m aid contribution, according to Pakistan's National Disaster Management Authority, though just $5m of this will be in cash, with the rest in the form of relief goods. The Saudi public has separately raised $19m. Muslim countries have been criticised for not giving enough to help victims of the disaster.
The UN announced today that eight million flood victims now need urgent humanitarian relief, while more than four million people have been made homeless. The flooding is still inundating new areas, with two or more weeks of the monsoon season yet to run, while the threat of disease means the crisis could grow much worse.
A second wave of flooding has hit the southern provinces of Sindh and Balochistan.
In Britain, the Disasters Emergency Committee has expressed "grave concern" that cholera cases have been confirmed.
A vast area slicing through the middle of Pakistan, running from the mountains of the north to the desert areas of Sindh in the south, has been affected. It is estimated that billions of dollars will be needed to rehabilitate the ravaged areas, rebuilding infrastructure and the economy.
The UN appealed last week for $460m to cover the first 90 days of the emergency. It said today that half the target had been reached, but warned that it was able to reach less than a quarter of the eight million people in urgent need of food and clean drinking water. The cost of providing clean water alone is about $2m a day.