The final sticking points involved complex talks led by Mnuchin and Ways and Means Chairman Richie Neal (D-Mass.) over sick leave for employees impacted by the coronavirus as well as their family members, said multiple Democratic and GOP aides.

Pelosi and Mnuchin held several conversations throughout Thursday. Pelosi then tapped Neal to try hammer out an accord over the paid leave issue with Mnuchin, said Democratic aides.

The multibillion-dollar House proposal — which aims to shore up safety-net programs like food aid and unemployment insurance — represents Washington's most aggressive response to the growing coronavirus crisis, which has sent financial markets into a panic as it quickly spreads across the globe. Schools across the United States announced closures throughout the day. The NCAA canceled its annual college basketball tournament, while businesses and state and local governments ordered their workers to stay home.

With so much at stake, Democrats and the White House are wrestling over two initiatives to help workers directly impacted by the coronavirus.

First, Democrats want to permanently require businesses to offer 14 days of paid leave directly to workers in the event of a public health emergency. But it also would include a refundable tax credit for employers with 500 employees or less to help offset those costs, reimbursed by IRS.

The second is a proposed temporary federal sick leave program. Workers suffering from the coronavirus, or with family members who have it, would receive some portion of their current wages for up to three months.

Both of the programs would be tied to the length of the coronavirus outbreak, which makes it hard to predict their cost.

Reps. Rosa DeLauro (D-Conn.), Bobby Scott (D-Va.) and other lawmakers drafted the initial proposals.

Early Thursday, Republicans and the White House raised strong objections to the Democrats’ initiative, which was unveiled close to midnight on Wednesday. But Pelosi told reporters that Democrats have agreed to “most” of the GOP’s proposed changes.

The two sides had earlier reached agreement on a Medicaid cost-sharing provision, as well as a temporary liability waiver to mask manufacturers, according to sources in both parties.

Some progressive Democrats are concerned about concessions made by party leaders on paid sick leave. DeLauro, a vocal advocate on the issue, has continued to push for a provision that would allow permanent paid sick leave, despite objections from Republicans who want only temporary benefits.

Asked whether Democrats would need to drop their push for a permanent sick leave provision amid GOP resistance, DeLauro sought to downplay the controversy.

“This is all focused on coronavirus. This is what the emergency is,” DeLauro said. “Progress is being made. ... We’re trying to button it all up.” Still, even some of DeLauro’s Democratic colleagues have lost patience, with several privately complaining that her refusal to relent is a key obstacle to a bipartisan deal.

Even as Pelosi and Mnuchin continued their talks on the House bill, Senate Majority Leader Mitch McConnell declared his chamber would cancel next week's recess to continue work on dealing with the outbreak. If the House passes the bill Friday, the Senate could approve it next week and send it to President Donald Trump's desk.

"Notwithstanding the scheduled state work period, the Senate will be in session next week," the GOP leader tweeted. "I am glad talks are ongoing between the Administration and Speaker Pelosi. I hope Congress can pass bipartisan legislation to continue combating the coronavirus and keep our economy strong."

Senior Democrats had initially been hopeful — some, even confident — that their bill would immediately win support from Republicans.

By Thursday morning, however, GOP leaders said they would oppose the plan over the paid leave plan and changes to Medicaid, which would help hospitals cover swelling costs of uninsured patients.

House Minority Leader Kevin McCarthy (R-Calif.) told Republicans on a conference call Thursday morning that the GOP is going to oppose the Democratic coronavirus bill as currently constructed, according to sources on the call. At a press briefing shortly after, McCarthy said both chambers should remain in session until a bill can be negotiated, repeatedly emphasizing that they want to work with Pelosi.

“I think we stay here, we get it right,” McCarthy told reporters. “I think we can get this done in the next 48 hours."

Republicans have specifically taken issue with language in the bill that requires paid sick leave for all businesses with no exemptions or end date, puts the Social Security Administration in charge of the paid emergency leave program and increases Medicaid’s Federal Medical Assistance Percentage.

Trump also said Thursday that he did not support the measure, even as his Treasury chief took part in multiple conversations with Pelosi to discuss changes to the bill.