The United States is teetering on the brink of a federal government shutdown, as hard-right Republicans in Congress have rejected a last-ditch effort to keep offices open when the new budget year begins Sunday.

Senators are slated to be at work in a rare Saturday session, in an attempt to approve temporary funds. But that effort may be too late.

So what exactly happens if a deal isn’t in place by midnight?

A U.S. government shutdown would disrupt many programs and services that Americans rely upon.

Federal workers would face furloughs, and over 2 million active-duty and reserve military troops would work without pay.

Social Security checks would still continue to go out, but other government functions would be significantly curbed if the shutdown happens Sunday.

Federal agencies would cease all actions that are deemed nonessential.

People applying for government services such as passports, firearm permits and clinical medical trials could see delays.

Head Start programs serving over 10,000 disadvantaged children would immediately lose federal funding.

National parks would close on Monday.