President Donald Trump said Tuesday that a $2 trillion infrastructure package should be part of Congress’ next response to the coronavirus pandemic, reviving a 2016 campaign pledge to ramp up construction projects despite public health guidance that Americans should stay home and isolated to the greatest extent possible.

Citing extraordinarily low interest rates that have reduced the cost of federal borrowing, Trump said on Twitter that now “is the time” to push forward with an infrastructure package in response to the severe economic downturn caused by the coronavirus. Numerous House Democrats have also discussed in recent weeks advancing infrastructure legislation as part of their response to the coronavirus.

“With interest rates for the United States being at ZERO, this is the time to do our decades long awaited Infrastructure Bill,” Trump wrote on Twitter. “It should be VERY BIG & BOLD, Two Trillion Dollars, and be focused solely on jobs and rebuilding the once great infrastructure of our Country! Phase 4.”

But lawmakers for more than three years now failed to break meaningful ground on bipartisan infrastructure talks, making the issue something of a long-standing joke on Capitol Hill. And some experts pointed out a pandemic may be a poor time to ramp up construction projects, given that federal health officials are urging workers to stay home if possible and avoid personal contact.

His “Phase 4” comment refers to the fact that Congress has passed three laws since the outbreak of the coronavirus, with the most recent one enacted Friday. That law directs more than $2 trillion in spending for emergency assistance to companies, new $1,200 payments to millions of Americans and assistance for airlines, state unemployment programs and a host of other groups.

The president offered no additional specifics about his infrastructure idea, and a White House spokesman did not immediately respond to a request for more details.

But congressional Democrats are at work on the next effort — the fourth package to be taken up by Congress to respond to the outbreak — and discussions have begun on what it may include.

Treasury Secretary Steven Mnuchin and House Ways and Means Committee Chairman Richard Neal, D-Mass., stepped up talks on an infrastructure deal in February, but those negotiations were derailed by the widening impact of the coronavirus.

Public health experts have called for Americans to self-isolate, and numerous states including Minnesota have issued “stay-at-home” orders urging all but essential personnel to remain in their homes. Infrastructure talks have largely centered on providing hundreds of billions for maintenance and repair work on the nation’s roads, bridges and other decaying infrastructure — all of which would likely require workers to be in close contact with one another.

“I’ve been making this point for years now: He’s correct,” said Jared Bernstein, former economic adviser to former Vice President Joe Biden, about Trump’s argument about the potential to use low interest rates to fund a large infrastructure bill. “But we have to be realistic about how infrastructure fits into the nature of the current crisis.”

That issue may not be impossible to resolve. Congress should pass an infrastructure package now to capitalize on the political crisis and low interest rates, but that construction projects should not begin until quarantines are lifted, said Peter Gowan, an economic expert at the left-leaning Democracy Collaborative.

Other outstanding fissures may still be difficult for lawmakers to overcome. Senate Republicans have balked at raising taxes as part of an infrastructure deal, a key sticking point in previous negotiations, and it is unclear if conservatives are willing to spend more money beyond the large deals signed into law. Trump’s reference to low interest rates on Tuesday suggested he’s in favor of borrowing heavily in order to finance new projects, which would likely add to the government’s debt.

During his campaign four years ago, Trump promised a $1 trillion infrastructure package that he said would create hundreds of thousands of jobs and rebuild roads, bridges, ports and airports, among other things. But White House officials could not reach agreement among themselves over how to finance such a package.

Congressional Democrats have long been skeptical of the seriousness behind Trump’s attempts. And both sides have sharply disagreed about what projects should be included in an infrastructure bill, with conservatives rejecting Democratic efforts to include clean energy projects and other provisions aimed at mitigating climate change in their legislation.

“We all make the jokes about it, but the problem is infrastructure is an empty vessel term that means different things to different people,” said Ryan Ellis, a conservative tax expert. “You can talk to 10 people around town and you may get 10 different emphases for what that means and what the definition of it is.”