The World Bank said it would provide as much as $200 million in emergency funding to help Liberia, Sierra Leone and Guinea.
"I am very worried that many more lives are at risk unless we can stop this Ebola epidemic in its tracks," World Bank President Jim Yong Kim said in a statement. "The international community needs to act fast to contain and stop this Ebola outbreak," he added.
African Development Bank President Donald Kaberuka told Reuters that his bank would immediately disburse funds to the three countries, whose health systems and resources have been strained by the outbreak. The worst outbreak of Ebola ever has killed nearly 900 people since it began in February.
Bank officials said the funding was close to $60 million.
"These countries need structural support to build up their health systems" still recovering from years of conflict, Kaberuka said. "We have the science, we have the ability, and the means to contain this thing. I am confident of that," he said.
The funding is in response to a $100 million plan launched by the World Health Organization last week to tackle the epidemic. WHO chief Margaret Chan said on Friday that Ebola was outpacing efforts to contain it and warned of "catastrophic" consequences if the situation deteriorated.
The United States will also provide more help to the affected countries and to international agencies responding to the outbreak, providing equipment and technical expertise, State Department spokeswoman Jen Psaki said on Monday.
Senior State Department officials met with Guinean President Alpha Conde and representatives from Liberia and Sierra Leone to discuss U.S. support.
"The group identified national and regional priorities and held intensive discussions on the types of assistance needed to mount an effective response," the State Department said.
Liberia and Sierra Leone's presidents canceled their plans to attend the summit to deal with the outbreak at home, although they have sent delegations to the meetings.
The nearly 50 African leaders are attending the economic, security and diplomatic summit through Wednesday.
U.S. President Barack Obama said on Friday that the United States was "taking the appropriate precautions" and that some participants at the summit would be screened for exposure to the virus.
A second American aid worker who contracted the hemorrhagic virus while helping fight the disease in West Africa was expected to arrive in Atlanta on Tuesday, according to Christian mission group SIM USA.
Sierra Leone and Liberia deployed hundreds of troops on Monday under an emergency plan to fight the spread of the virus.
The outbreak began in the forests of remote eastern Guinea in February.