The funds will be used by U.N. and non-governmental organizations to bring in additional doctors, medicines and water-purification equipment to treat up to 200,000 people who could show cholera symptoms ranging from mild diarrhea to severe dehydration, the global body said.
"We absolutely need this money as soon as possible," said Elisabeth Byrs, a spokeswoman for the U.N. humanitarian office.
She told reporters in Geneva that the funds need to be provided quickly "otherwise all our efforts can be outrun by the epidemic."
At least 11,125 cases of cholera have been confirmed in five of Haiti's 10 districts since the outbreak began last month. Ten deaths and 278 cases have occurred in the capital Port-au-Prince.
The World Health Organization said Friday that the epidemic isn't likely to end soon.
"The projections of 200,000 cases over the next six to twelve months shows the amplitude of what could be expected," said WHO spokesman Gregory Hartl. He noted that the current fatality rate of 6.5 percent is far higher than it should be.
"No one alive in Haiti has experienced cholera before, so it's a population which is very susceptible to the bacteria," Hartl said. "Once it is in water systems it transmits very easily, and it transmits among people who are often asymptomatic."
"Cholera, now that it is in Haiti, probably the bacteria will be there for a number of years to come," he added. "It will not go away."
The cause of the outbreak in Haiti is still unknown. The country hadn't seen cholera cases for decades before last month.
"The specific origin of this specific outbreak is something which probably will be investigated at some point, but what is important right now is the response on the ground," Hartl said.