The World Health Organization has received only $3 million of the $56 million needed to fight the Zika virus from its member countries, officials said Tuesday.

The WHO has asked for $25 million for its own efforts to fight Zika during the first six months of the year. Those efforts include sending staff to countries grappling with the disease and organizing scientific meetings, said Margaret Chan, the WHO's director-general. The other $31 million would go to other groups, including nonprofits.

"Financial support . . . is truly a big challenge for us," Chan said. "We cannot allow money to be the barrier to do the right thing. The public health implications for so many countries, for so many families, is so huge."

The WHO is in "active discussion" with its member countries on an additional $4 million to fight Zika, Chan said.

Until more money materializes, Chan said she will try to move money around the WHO to free up resources to fight Zika. About 20% of the WHO budget is flexible and can be used for any purpose. Still, Chan said she doesn't want to take money away from other important issues, such as treating and preventing HIV.

"If money continues to not come in, I don't know how long we can continue like this," Chan said.

President Obama also has faced opposition to his funding requests on Zika.

Obama has asked Congress for $1.8 billion to fight the Zika virus at home and abroad. Congressional Republicans have been reluctant to approve that funding, arguing that the White House should tap unused money allocated for Ebola instead.

Leaders of the Centers for Disease Control and Prevention and the National Institute of Allergy and Infectious Diseases have publicly said that the lack of secure funding could endanger their efforts to fight the disease.

WHO officials have predicted that there could be 4 million cases of Zika in the Americas this year.

Brazil has been hardest hit by Zika. The country first reported Zika infection last May, which was followed by a dramatic increase in normally rare birth defects.

In recent months, Brazil has reported 6,480 suspected cases of microcephaly, in which babies are born with abnormally small heads and, in most cases, brain damage, said Anthony Costello, director of the WHO department for maternal, newborn, child and adolescent Health. Brazil has investigated 2,212 of the cases and has confirmed 863 of them, or about 39%. Most of those cases have been reported in northeastern Brazil.

At that rate, Brazil could see 2,500 cases of microcephaly, Costello said. Brazil normally has only about 150.

Panama also has reported its first case of the condition to the WHO, Chan said. The case was a baby born at 30 weeks gestation, about 10 weeks premature. The baby died a few hours after birth. Tests found the Zika virus in its umbilical cord.