Congressional negotiators may be nearing an agreement on funding to help fight the spread of the Zika virus.

Members and staff from the House and Senate Appropriations committees have been meeting behind closed doors since last week to in hopes of reaching a compromise between a bipartisan Senate bill that would provide $1.1 billion to fight the virus through September 2017 and House legislation that would provide $622 million through the end of the year. The House-Senate talks have proceeded quickly and negotiators may reach an agreement as early as Tuesday afternoon, according to aides.

Sen. Patty Murray, (D-Wa.), who helped write the Senate legislation, on Tuesday pressed for her fellow negotiators to finish their work and adopt the Senate-passed language.

“This package has support on both sides of the aisle,” Murray said on the Senate floor. “With the health and well-being of women and babies on the line, now is not the time for nickle and dime-ing,” Murray said. “There is no reason we can’t get a strong emergency funding proposal to the president’s desk this week.”

Both congressional proposals fall short of the $1.9 billion requested by President Obama — but White House officials are less critical of the Senate figure. Last month, Deputy White House Press Secretary Eric Schultz left the door open for Obama to accept the Senate bill.

“They made more progress in the Senate than they did in the House,” Schultz said. “I’ll remind you that the Senate bill is bipartisan.

Pressure is mounting for Congress to reach a deal as most states are approaching the height of mosquito season. Zika has been linked to birth defects and health issues across Latin America and the Caribbean, including parts of Mexico and Puerto Rico.

Last week, the Centers for Disease Control announced that three women in the U.S. mainland have delivered babies with birth defects caused by Zika and three more lost or terminated pregnancies as a result of brain damage from the virus. The CDC is currently monitoring 234 women on the U.S. mainland and another 189 in Puerto Rico.

Senate Republican Vice Chair Roy Blunt (R-Mo.), another co-author of the Senate legislation, told reporters Monday he was optimistic the talks would wrap up quickly but he warned that House Republicans were still reluctant to accept the Senate bill.

“I feel good about where we are,” Blunt said. “The issues are all still largely the same issue but I think they are all approaching something we can agree on.”

Blunt, a key Senate negotiator, said the talks were still stuck on how large the spending package should be and whether cost should be balanced out with reductions elsewhere in the budget. House Republicans want to offset any new spending with funds leftover from fighting the Ebola virus as well as cuts to the Department Health and Human Services administrative budget.

The White House has already moved to divert $589 million from the Ebola early response fund to Zika, and most Democrats say that moving any additional money out of that fund could make it harder to respond if Ebola re-emerges.

“We ought not be reducing Ebola funds and the effort to continue to contain Ebola in order to fight Zika,” House Minority Whip Steny Hoyer (D-Md) told reporters on Tuesday.

Democrats have insisted that funding for health emergencies, like Zika and Ebola, needs to be expedited regardless of whether cuts can be found elsewhere in the budget to compensate.  Sen. Barbara Mikulski (D-Md.), the top Democrat on the Appropriations Committee, said Monday that the fight had come down to those offsets and whether to include restrictions on how the Zika money could be spent.

“We are still arguing the need for emergency funding with no restrictions,” Mikulski. “If you want emergency funding there are no offsets.”