ISLAMABAD (Agencies) The United Nations warned Monday that up to 3.5 million children were at risk from water-borne diseases in Pakistans floods and said it was bracing for thousands of potential cholera cases. Fresh rains threaten further anguish for millions of people that have been affected by the countrys worst floods for 80 years and UN Secretary-General Ban Ki-moon has urged the world to speed up international aid urgently. Described as the worst humanitarian crisis in the world today, the three-week disaster has affected 20 million people, and has destroyed crops, infrastructure, towns and villages, according to the government. Maurizio Giuliano, spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA), feared that Pakistan was on the brink of a second wave of deaths unless more donor funds materialised. Up to 3.5 million children are at high risk of deadly water-borne diseases, including diarrhoea-related, such as watery diarrhoea and dysentery, he said, estimating the total number at risk from such diseases at six million. Typhoid, hepatitis A and E are also concerns, he said. WHO (World Health Organisation) is preparing to assist up to 140,000 people in case there is any cholera, but the government has not notified us of any confirmed cases, the spokesman told AFP. We fear were getting close to the start of seeing a second wave of death if not enough money comes through, due to water-borne diseases along with lack of clean water and food shortages, he said. One charity worker, speaking on condition of anonymity, told AFP that several flood survivors had already died of the disease. At the weekend a shocked Ban became the first world leader to visit the flood-affected areas, saying he would never forget the heart-wrenching scenes of destruction and suffering that he had witnessed. A senior Red Cross official said rebuilding Pakistan after the worst floods in decades could take five years. Crops are gone. Infrastructure is gone, including canals. Community canals. Irrigation canals. To bring that back is going to take a long time. It could end up being five years, said Bekele Geleta, Secretary-General of the International Federation of Red Cross and Red Crescent Societies (IFRC). United Nations International Children Emergency Fund (UNICEF)s Regional Director for South Asia, Daniel Toole on Monday appealed to international community and UN donor agencies to urgently support Pakistan for the assistance and rehabilitation of over 20 million people affected by a large scale and record-breaking flood of its history. Foreign and Pakistan government, donor organisations and all the stakeholders need a lot to do to help out such a large number of people affected by the recent devastated flood and urgent support of international community is extremely vital for provision of food, medicines, shelters to flood victims, Toole told journalists after visiting relief camps at Charsadda district on Monday. He arrived Khyber Pakthunkhwa to see the impact of recent floods on people and review UNCIEFs support for the hundreds of thousands of children and women in one of the worst hit provinces of Pakistan. He said UNCIEF was closely working with Pakistan in collaboration with UN agencies and other humanitarian partners to provide a lifeline for the most vulnerable children and women, yet we must all work together to reach out to the inaccessible with the utmost speed. It is also the responsibility of Pakistani people to respond and come for help of their displaced brothers in this hour of need in holy month of Ramazan as many people still require food and water in upper parts of Khyber Pakhtunkhwa, he added. The international community and UNCIEF are with Pakistanis and we are here to mobilise support for millions of flood affected people of Pakistan. He said UNICEF was providing help, healthcare and clean drinking water facilities, critical medical supplies, supplementary food, family hygiene kits and other non-food items to over one million affected people in Khyber Pakhtunkhwa and we need to do much more for them.