The Senate voted Wednesday to approve an earlier package passed March 14 by the House of Representatives, which President Donald Trump then signed late Wednesday.
The package includes up to $300 billion in loans for affected small businesses and $50 billion in loans to the airline industry, with some restrictions, with another $150 billion available for loans or guarantees to other economic sectors severely impacted by the outbreak.
Another $250 billion would go directly to American taxpayers on a means-tested basis starting April 6, with a second $250 billion round scheduled for May 18.
The proposal from the Treasury Department also calls for temporarily using a federal emergency stabilization fund to backstop money market mutual funds.
Senate leaders pledged to act quickly on the proposal.
The Senate voted Wednesday to approve an earlier package already approved March 14 by the House of Representatives. The House package, called Phase 2, expands free testing, extends sick leave benefits and provides $1 billion in food aid to the most vulnerable populations.
A third package is expected to be negotiated shortly.
On Tuesday, Treasury Secretary Steven Mnuchin approved the Federal Reserve Board's Commercial Paper Funding Facility to provide liquidity to the financial system, including short-term credit to businesses.
At a White House briefing Wednesday, President Donald Trump disputed Mr. Mnuchin's estimate that unemployment could soon reach 20%.
Mr. Trump said at the briefing that he has invoked the Defense Production Act, allowing his administration to pressure American manufacturers to accelerate production of ventilators and other medical supplies needed to fight the coronavirus pandemic. Vice President Mike Pence said the industry is showing "tremendous spirit" to ramp up production.
Mr. Pence confirmed there are now coronavirus cases in all 50 states and the U.S. border with Canada is temporarily closed to non-essential travel.
Asked whether his administration would invoke a nationwide travel shutdown, Mr. Trump said, "It's a war. We want to make sure they all stay together, so that after the war is won, we can go right back."