Pakistan has accepted $5m (£3.2m) in aid from its rival and neighbour India, as donors pledged more money for the flood-hit country.
Abdullah Haroon, Pakistan's UN Ambassador, welcomed the offer saying the disaster transcended any differences the two countries had.
Meanwhile, officials say the province of Sindh is now the worst hit, with more than two million people affected.
New warnings are being issued and villages evacuated, they said.
Mr Haroon welcomed the latest offers of help, which followed a two-day special meeting of the UN Security Council in New York to discuss the crisis.
The UN says it has now raised about 70% of the $460m it called for in its emergency appeal.
Mr Haroon described the new donations as "indeed heartening" and "a good beginning", but added that Pakistan will need support for years to come.
India's UN Ambassador, Hardeep Singh Puri, said the donation of $5m in relief supplies was an initial offer and his country was ready to do more if needed.
"We are willing to do all that is in our power to assist Pakistan in facing the consequences of floods," he said.
"We extend our wholehearted support to the government of Pakistan in its efforts for relief and rehabilitation of the... population."
The offer came after Indian Prime Minister Manmohan Singh spoke to his Pakistani counterpart Yusuf Raza Gilani on Thursday.
Pakistan and India have slowly been improving ties since the Mumbai militant attacks of 2008 put relations between the two nuclear-armed rivals at a new low.
The floods began last month in Pakistan's north-west after heavy monsoon rains and have since swept south, swamping thousands of towns and villages in Punjab and Sindh provinces.
About one-fifth of Pakistan's territory is underwater and an estimated 20 million people are affected.
Officials estimate that about 1,600 people have been killed.
In the southern province of Sindh, hundreds of thousands of people have been left homeless as the Indus river overflowed, swamping homes and valuable farmland.
"Everything has been wasted. Nothing is left," said Qasim Bhayyo, 45, a refugee from Qayyas Bhayyo village in Sindh.
"I saw my house of wood and mud washed away. I saw grain and flour - we stockpiled food for months. It was all destroyed. We had no way to save our goats and buffaloes stranded in the water and crying."
As aid agencies stepped up the relief effort, the UN said on Friday that more helicopters were urgently needed to reach communities cut off by the water.
Experts warn of a second wave of deaths from water-borne diseases such as cholera unless flood victims have access to supplies of fresh drinking water.
If you would like to make a donation to help people affected by the floods in Pakistan, you can do so through the UK's Disasters Emergency Committee at www.dec.org.uk or by telephone on 0370 60 60 900.