The rapidly spreading Zika virus -- which can be transmitted sexually and by mosquitos -- is most dangerous for pregnant women. But Republicans in Congress on Thursday released a funding proposal limiting the distribution of contraceptives and preventing family planning organizations like Planned Parenthood from participating in the effort to help women in Zika-affected areas delay pregnancy.

The House passed a proposal that allocates $1.1 billion to fight the Zika virus -- just over half the amount the Obama administration requested four months ago to stop the epidemic.

Democrats are furious that Republicans short-changed the president's funding request. They are particularly upset that the bill excludes $50 million in requested funds for maternal and child health and blocks supplemental funds from going to Planned Parenthood for birth control services. The bill mandates that the Zika funds be prioritized for mosquito control programs, vaccines and diagnostics, leaving no resources for contraceptives or condoms.

"It is unthinkable that in the face of a public health emergency, Republicans chose to pass a hyperpartisan proposal that doubles down on using women’s health as a political football by restricting access to women’s health care, like contraception, which is especially critical to preventing the spread of this virus," said Sen. Patty Murray (D-Wash.), ranking member on the Senate Health Committee.

Zika has been linked with the birth defect microcephaly, which causes babies to be born with underdeveloped brains and abnormally small heads. Several countries are advising women to delay pregnancy while the threat of Zika looms, which has increased the demand for abortions and put a spotlight on the need for effective family planning.

Planned Parenthood said the GOP policy "mocks the seriousness of this looming public health crisis," which has already afflicted thousands of babies across South and Latin America -- and one so far in the continental United States.

"In the face of threats to the public, elected officials have a responsibility to rise above politics and take meaningful action," said Dana Singiser, a Planned Parenthood executive. "Instead, Republicans have once again reverted back to the same agenda we have seen time and time again of attacking women’s health care. It is just common sense that women need more access to basic family planning at home and abroad in the face of Zika, not less."

House Speaker Paul Ryan (R-Wis.) said the bill would sufficiently address the crisis.

“It is a responsible plan that assures the administration will continue to have the needed resources to protect the public,” he said.

Democrats vowed to block the bill from passing until Republicans agree to a more robust and comprehensive solution. The White House also condemned it on Thursday.

"It is clear that once again, Republicans have put political games ahead of the health and safety of the American people, particularly pregnant women and their babies," Press Secretary Josh Earnest said. "This plan from congressional Republicans is four months late and nearly a billion dollars short of what our public health experts have said is necessary to do everything possible to fight the Zika virus, and steals funding from other health priorities."