ISLAMABAD--.UN Secretary-General Ban Ki-moon has urged the "the world community to speed up...assistance to the Pakistani people." Ban made the appeal shortly after his arrival in Pakistan. The UN says it has received 20 per cent of the $460 million it has requested in emergency aid. Prime Minister Yousuf Reza Gilani said the floods triggered by monsoon rains had affected 20 million people. Aid worker say 6 million people need humanitarian assistance. UN officials have confirmed the first case of cholera in Mingora, in the northwestern district of Swat. Other cases of the deadly disease are suspected. Aid workers are also treating thousands of cases of acute watery diarrhea. The government canceled independence day celebrations Saturday in Pakistan, where authorities say the floods have killed 1,600 people. Washington has provided more than $76 million in relief aid to Pakistan. U.S. helicopters have evacuated 4,000 people and delivered close to 170 tons of relief supplies. Nearly half the country has been inundated, causing loss of crops and, in some areas, wiping out 80 per cent of farm animals.