Fuelled by infighting among Republicans in the House of Representatives over Spending cuts, the United States is barreling towards a Government shutdown. Lawmakers in the US Congress have until 30 September (the end of the fiscal year) to reach an agreement over how to keep money flowing to federal agencies, or the government will have to close many of its doors and furlough staff — including tens of thousands of scientists — without pay. Depending on how long the shutdown lasts, work at science agencies will stop, interrupting experiments, delaying the approval of research grants and halting travel to scientific conferences.

The shutdown drama is unfolding in the House, where the Republican party holds a narrow majority. A handful of extreme right-wing Republicans are refusing to support a ‘continuing resolution’ to fund the government temporarily while negotiations over a 2024 budget continue — that is, unless Congress agrees to drastically cut government spending, among other demands. Democrats are united in opposition to their requests, and most Republicans in both the House and the Democrat-controlled Senate are looking for compromise that would keep the government open. But time is running out.

Here Nature takes a look at what’s driving this latest budgetary crisis, and what’s in store for scientists if the US government shuts down next week.

How did we get here?

This is basically a continuation of the US debt-ceiling crisis, which occurred less than four months ago. At that time, some Republicans threatened to block legislation that would make sure the government had enough money to pay its bills, unless Democrats, including President Joe Biden, agreed to future spending cuts. Congress avoided disaster by reaching a bipartisan agreement to limit federal ‘discretionary’ spending — money that goes to US science and other programmes. The legislation, which broadly outlined reductions in spending over the next two years, was signed by Biden on 3 June.efficiency, making progress on a series of annual bills that outline detailed spending levels for federal agencies. The irony is that lawmakers haven’t made this much progress by the fiscal-year deadline in a long time, says Jennifer Zeitzer, who leads the public-affairs office at the Federation of American Societies for Experimental Biology (FASEB), based in Rockville, Maryland. “And yet here we are, staring down the barrel of another shutdown.”

Normally, Congress would pass a resolution to continue funding agencies for a couple of months while lawmakers finish up budget negotiations, but the situation is different this year. Republicans hold only a narrow majority in the House, occupying 222 seats, compared with the Democrats’ 213. That means that to pass legislation, the Republican party needs to maintain a united front and vote nearly in unison, to overcome Democratic opposition. Several hardline Republicans are holding out, however, using their leverage to force further concessions on spending.

What happens if the government shuts down?

The answer differs from agency to agency. Some agencies have residual funds that they can tap to continue operating in the short term. And to varying degrees, all agencies maintain a skeleton staff of ‘essential’ workers to complete duties related to national security and the protection of public property, for instance.

The US National Science Foundation (NSF), expects to halt work for 1,487 out of its 1,946 employees, once short-term funding runs out, for example. Scientists can continue to submit applications for funding to the agency, which pays for about one-quarter of the taxpayer-supported basic research in the United States, but no new projects will be approved. The Department of Health and Human Services, which houses the US National Institutes of Health, a significant funder of biomedical research, plans to furlough some 37,325 people — 42% of its staff — by the second day of a shutdown. ’Essential’ staff working at its clinical centre or on public-safety missions such as monitoring for viral outbreaks will continue to report to work.