WASHINGTON — The federal government entered a partial shutdown early Saturday after Congress failed to pass legislation in time to keep a swath of departments and agencies open.

The shutdown is expected to be brief and have little impact, however, as Senate leaders announced they have a deal to vote on a funding package in the early hours of Saturday morning.

The House voted Friday morning to pass a $1.2 trillion spending bill funding the departments of State, Defense, Labor, Health and Human Services and Homeland Security, among others. But amid Republican demands for amendments, the Senate was unable to reach an agreement to hold a speedy vote ahead of a midnight deadline to fund those departments.

The Senate indicated it has sufficient support to get the bill across the finish line following a 78-18 procedural vote on Friday that advanced the measure. Senate Majority Leader Chuck Schumer, D-N.Y., announced just before the deadline that both parties have an agreement to vote on multiple amendments and then final passage of the bill early Saturday morning.

Barring unforeseen problems, the shutdown would have very little impact. If it dragged on through Monday, it would trigger furloughs and suspension of various federal services, with “essential” workers like air traffic controllers and TSA agents working regardless.

“It’s been a very long and difficult day, but we have just reached an agreement to complete the job of funding the government,” Schumer announced on the Senate floor just before midnight. “It is good for the country that we have reached this bipartisan deal.”

The divided Congress has narrowly averted multiple shutdowns this session, passing four stopgap bills that kept extending the deadline. And at nearly six months into the fiscal year, it’s unusually late in the game to be haggling over the funding measures. The latest bill was released Thursday and passed by the House on Friday morning, leaving little time for the Senate to act.

In order to vote quickly on legislation, all 100 senators must agree to speed up the process, and senators typically agree to a group of messaging amendment votes to reduce the amount of procedural time required to complete consideration of a bill.

Those talks appeared to fall apart mid-day Friday, with Sen. Tom Cotton, R-Ark., arguing the agreement was scuttled by vulnerable Democrats in key Senate races, claiming they don’t want to have to vote on amendments that could be used against them in their re-election campaigns.

“The bottom line is Democratic senators running for re-election are scared to vote on amendments,” Cotton told reporters, adding without providing evidence: “Jon Tester has said that he would rather have the government shutdown and vote on Sunday night then vote on these amendments for you.”

But Tester, a Democrat who is in a tight re-election race in the red state of Montana that could determine the Senate majority, fired back, telling NBC News, “That’s bulls—.”

The back and forth came to a head when the two senators were talking to different groups of reporters just feet away from each other off the Senate floor.

“Did Cotton say that they’re holding amendments because of Jon Tester?” Tester yelled at Cotton during the exchange. “Because if he did, he might be full of something that comes off the back of a cow.”

Senators were frustrated by the fact that Congress was able to repeatedly avert funding lapses during this fiscal year alone, but struggled to do so on the final one of this fiscal year.

“It makes me ill,” Sen. Lisa Murkowski, R-Alaska, said in an interview, adding that she felt “like I’ve had too much sugar and bad pizza” after Senate Republicans were served those items for lunch.

“If we had had salmon, we would have been thinking because it’s like we’ve all those fine omega 3s,” she said. “We’re just like — we’re a mess of a candy pizza muddle, we’re operating like teenage boys.”

“A failure to fund the government tonight means everyone loses, and everyone loses a lot,” Sen. Richard Blumenthal, D-Conn., told reporters. “There’s no winner to come out of a catastrophe like failing to fund the government.”

“You know, you can be pretty critical of the House and the House leadership, but the House figured out how to move a bill today,” Murkowksi said on Friday. “The House is not going to be responsible for a government shutdown, it will be on the United States Senate. We know better than this.”