WASHINGTON — Faced with Republican resistance after asking for billions of additional dollars to keep fighting the coronavirus, the Biden administration recently supplied Congress with a chart showing how much money it had left for testing, therapeutics and vaccines. It was filled with zeros.

But on Wednesday, Democrats in Congress stripped a $15.6 billion emergency aid package from a broader spending bill amid disputes over how to cover the cost. The move injects uncertainty into President Biden’s plan, announced last week, to address “urgent needs” in his pandemic response and to prepare for future variants.

With Republicans blocking new spending on the pandemic, Democrats had agreed to take the emergency aid from existing programs — including $7 billion that states had been counting on for their own pandemic response. That led governors to protest, rank-and-file lawmakers to balk and Speaker Nancy Pelosi to plan on passing the coronavirus funding package separately, a risky move given Republican opposition to new federal spending in the evenly divided Senate.

White House officials say the money is desperately needed to continue to secure supplies of essential treatments for Covid-19 and to develop next-generation vaccines. Jen Psaki, the White House press secretary, laid out the administration’s predicament in dire terms at a news briefing last week.

By May, she said, the current supply of monoclonal antibody drugs used to treat Covid will “stock out.” By July, the administration will run out of another antibody drug, Evusheld, that was recently authorized to prevent Covid in people with immune deficiencies. Money is needed this month, she said, to contract with drug makers so there is no gap in deliveries.

“Let me be very clear,” Ms. Psaki said. “This is an urgent request.”

Over the past two years, Congress has appropriated more than $370 billion in pandemic response funds to the federal Department of Health and Human Services. The bulk of that money has been directed to health care providers; less than half, about $140 billion, was for testing, therapeutics and vaccines.

The administration’s spending chart, obtained by The New York Times, shows that all of the money has been spent or is already spoken for. (That includes spending by the Trump administration.) The Biden administration had initially asked Congress for $22.5 billion in additional pandemic aid, including $12 billion for procuring treatments and vaccines and $4.25 billion to support the global pandemic response; Congress whittled the request down $15.6 billion.

A White House spokesman, Kevin Munoz, warned on Wednesday that if Congress did not appropriate more funds, there would be consequences beyond the loss of antibody treatments. He said testing capacity would decline in March and the fund that pays for Covid testing and treatments for tens of millions of uninsured Americans would run out of money in April.

“Failing to take action now will have severe consequences for the American people,” Mr. Munoz said.

What happens next is unclear. House Democrats, switching gears at the last minute, abandoned a plan to vote Wednesday evening on a stand-alone bill to approve the coronavirus aid, which would be partially offset with some unspent pandemic funds without touching the state and local aid. Unless the bill is fully paid for, it is likely to face a dim future in the Senate, where 10 Republican votes are needed to pass most bills.

A group of three dozen Republican senators, led by Mitt Romney of Utah, told the White House last week that they would not consider billions in new Covid relief spending without a more detailed accounting of how earlier allocations had been spent and whether any money was left.

“It is not yet clear why additional funding is needed,” they wrote in a letter to Mr. Biden.

Public health experts, many of whom expect a new coronavirus variant to emerge at some point, were aghast at Wednesday’s developments. They worried that the rapid decline in coronavirus cases was giving rise to a false sense of security on Capitol Hill.

New virus cases in the United States have plunged in recent weeks, but about 1,500 Americans are still dying from the virus each day on average.

“Hopefully this is a procedural action, because if not, this is playing with infectious-disease fire,” said Michael T. Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

“This should be a déjà vu moment all over again,” he added. “It was a year ago right now that we were beginning to declare independence from Covid and we were certain that we were hitting that endemic period. Society learned that the virus wasn’t done with us yet.”

This week, a group of independent health experts who have been advising the White House, including Dr. Osterholm, issued their own pandemic preparedness plan, which they called a “road map for living with Covid.” The group’s leader, Dr. Ezekiel Emanuel, has estimated that it will cost $100 billion or more to fully prepare the nation for future variants and pandemics moving forward.

Adriane Casalotti, the chief of government and public affairs for the National Association of County and City Health Officials, also said more money was needed.

“The funding deal on the table was really focused on procuring commodities — tests, vaccines and treatments — which is critical, but did not include resources to drive consumer awareness and demand so that they reach those who need them,” she said. “We hope negotiators can come back to the table to find a way forward to fund the full range of Covid-19 response needs.”

Some governors, upset that Congress was planning to take away some of their pandemic response money from last year’s $1.9 trillion stimulus law, were happy with Wednesday’s developments. Gov. Asa Hutchinson of Arkansas, the chairman of the National Governors Association, said he was “very pleased” that the coronavirus supplement was removed from the bill.

Many states already had plans in place to spend the stimulus money that Congress wanted to divert, he said.

“Arkansas does not need to have additional Covid funds,” Mr. Hutchinson said. “But the last thing we need is to have the additional funds taken away that’s designed for broadband and other infrastructure needs.”

Mr. Hutchinson, a Republican, and Gov. Philip D. Murphy of New Jersey, a Democrat and the vice chairman of the National Governors Association, put pressure on lawmakers to preserve the funding for state and local governments and urged them to “negotiate in good faith” in a letter to congressional leadership on Tuesday.

Gov. Tony Evers of Wisconsin, a Democrat, also sent a letter to congressional leaders on Wednesday condemning the plan, which he said would cost his state about $225 million.

Brian Sigritz, the director of state fiscal studies at the National Association of State Budget Officers, said the initial spending plan could have slashed aid for 30 states that had not yet received their full share of the stimulus money. Under the plan, states would have received at least 91 percent of the $195 billion in total funding they were expecting.

And while Ms. Pelosi said earlier on Wednesday that localities would receive “no cuts,” local leaders had also expressed dismay with the proposal to scale back state funding, which they said would have ultimately affected cities and towns.

Emily Cochrane and Benjamin Mueller contributed reporting.