The United Nations general secretary Ban Ki-moon says emergency donations for Pakistan are now nearing $US560 million.The United States is the top donor, followed by Saudi Arabia and Britain. Mr Ban has praised the global community for its support, but has warned that the flood-stricken nation will face years of need. The country is now struggling to find shelter for an estimated four and a half people still camping under the open skies. The catastrophic floods swamped a fifth of Pakistan , an area the size of England, and affected a total of 20 million people in the country's worst natural disaster in living memory. Entire towns and villages were swallowed and now experts say it could take years to solve the shelter crisis. The United Nations says it does not have enough helicopters to deliver much needed aid to millions of flood victims in Pakistan . The UN World Food Programme says it has been trying to cover all of Pakistan with only 10 helicopters. More helicopters are scheduled to arrive, but the disaster is also widening.