WASHINGTON — Senate leaders raced to unravel last-minute snags Wednesday and win passage of an unparalleled $2 trillion economic rescue package steering aid to businesses, workers and health care systems engulfed by the coronavirus pandemic.

The measure is the largest economic relief bill in U.S. history, and both parties’ leaders were desperate for quick passage as the virus took lives and jobs by the hour. The Senate stayed in session in anticipation of still passing the bill after days of delays.

President Donald Trump implored Congress late in the day to move on critical aid without further delay.

The package is intended as relief for an economy spiraling into recession or worse and a nation facing a grim toll from an infection that’s killed nearly 20,000 people worldwide. Treasury Secretary Steven Mnuchin, asked how long the aid would keep the economy afloat, said: “We’ve anticipated three months. Hopefully, we won’t need this for three months.”

Underscoring the effort’s sheer magnitude, the bill finances a response with a price tag that equals half the size of the entire $4 trillion annual federal budget.

“A fight has arrived on our shores,” said Senate Majority Leader Mitch McConnell. “We did not seek it, we did not want it, but now we’re going to win it.”

“Big help, quick help, is on the way,” said Senate Minority Leader Chuck Schumer.

But the drive by leaders to speed the bill through the Senate was slowed as four conservative Republican senators demanded changes, saying the legislation as written “incentivizes layoffs” and should be altered to ensure employees don’t earn more money if they’re laid off than if they’re working.

Complicating the standoff, Sen. Bernie Sanders of Vermont, whose campaign for the Democratic presidential nomination has flagged, said he would block the bill unless the conservatives dropped their objections.

“What I am saying is that two can play the same game,” Sanders told The Associated Press. “This is most certainly not the bill that I or any other progressive would have written,” he said, but added that he supports it in the main, given the severity of the crisis.

Other objections floated in from New York Gov. Andrew Cuomo, who has become a prominent Democrat on the national scene as the country battles the pandemic. Cuomo, whose state has seen more deaths from the pandemic than any other, said: “I’m telling you, these numbers don’t work.”

Democratic presidential candidate Joe Biden said the package “goes a long way.” He said it will require strong oversight to ensure the wealthy don’t benefit at the expense of workers and proposed forgiving at least $10,000 of student loan debt as part of the federal response.

McConnell and Schumer hoped passage of the legislation in the Republican-led Senate would come by the end of the day.