The United Nations appealed for nearly $460 million Wednesday to provide immediate help to millions of victims of the worst floods in Pakistan in living memory and said it will need millions more to help rebuild the devastated country.Make no mistake, this is a major catastrophe, UN humanitarian chief John Holmes told diplomats from several dozen countries in launching the appeal. The affected population is estimated to be more than 14 million, almost one-tenth of Pakistan's population. The UN Office for the Coordination of Humanitarian Affairs, which Holmes heads, said at least six or seven million flood victims require immediate humanitarian assistance including shelter, food, clean water, sanitation and medical care. Before the $459.7 million appeal was launched, the UN already had pledges and commitments of more than $150 million but some $300 million is still needed, Holmes said. The US aim is to support Pakistan's relief effort to get aid as rapidly as possible to those in need, she said. According to the UN, over 1,200 people have died and at least 288,000 homes have been damaged or destroyed in the flooding. Pakistan's UN Ambassador Abdullah Haroon called the floods a particularly savage attack by nature and praised the United Nations for assisting in every way possible. But he said more help was needed and appealed especially for clean water to prevent cholera and assistance in dealing with snakebites, saying thousands of people have already been bitten. Haroon said the number of people affected could rise further because the floods are spreading and a week of further rains is predicted. He worried that as many as 16 million could be affected. Noting that the Asian tsunami in 2004 displaced less than 2 million people, Haroon said, This is seven times the amount. This is horrendous.