WASHINGTON — A divided House on Thursday approved legislation to keep the government funded through mid-February, but a group of Senate Republicans was still threatening to force a shutdown over the Biden administration’s vaccine and testing mandate for large employers.

With less than 36 hours before funding was set to lapse, the House voted 221 to 212 to keep the government open through Feb. 18 and provide $7 billion for the care and resettlement of Afghan refugees. Just one Republican, Representative Adam Kinzinger of Illinois, joined Democrats in voting for the measure.

But the fate of the legislation was uncertain in the Senate, where unanimity would be needed to expedite its passage before a midnight deadline on Friday. A few Republicans warned that they would object unless they were granted a vote on an amendment that would bar funding for carrying out President Biden’s vaccine and testing mandate for the private sector.

Leaders in both parties have warned against a government shutdown and have urged their colleagues to find alternative ways to register their opposition to the vaccine mandate. Multiple aides noted that the Senate was already on track to vote later this month on a Republican bid to roll back the rule.

“Let’s be clear: If there is a shutdown, it will be a Republican, anti-vaccine shutdown,” said Senator Chuck Schumer of New York, the majority leader. He added, “I hope cooler heads will prevail on the other side so we can keep the government funded before tomorrow’s deadline.”

Mr. Biden projected confidence that a shutdown would be avoided, telling reporters after a speech at the National Institutes of Health that he had spoken to both Senate leaders and that “there is a plan in place, unless somebody decides to be totally erratic.”

Senior Democrats and Republicans in Congress hailed the spending agreement, saying it would afford them more time to resolve outstanding disputes and approve longer-term legislation to fund the government next year. The House vote came just hours after leaders announced a bicameral agreement.

“While I wish the Feb. 18 end date were earlier, and I pursued earlier dates, I believe this agreement allows the appropriations process to move forward toward a final funding agreement that addresses the needs of the American people,” said Representative Rosa DeLauro, Democrat of Connecticut and the chairwoman of the House Appropriations Committee.

While lawmakers have long conceded that they need more time to negotiate the dozen bills that would fund the government for the entire fiscal year, the stopgap plan had become snarled in partisan disagreements over how long it should last and what additional funding proposals could be attached to it.

Because the short-term legislation maintains existing funding levels, it will effectively codify through mid-February spending levels that were negotiated with the Trump administration. Democrats had pushed to do so only through late January, as they are eager to enact their own funding levels and priorities while in control of the White House and both chambers of Congress.

Facing objections from Republicans, Democrats also dropped a push to avert billions of dollars in looming cuts to Medicare, farm subsidies and other programs.

Both parties agreed to provide $7 billion for Afghan evacuees who fled the country after the Taliban regained control and American troops withdrew. The additional funding includes about $4.3 billion for the Defense Department to care for evacuees on military bases, $1.3 billion for the State Department and $1.3 billion for a division of the Department of Health and Human Services to provide resettlement and other services, including emergency housing and English language classes.

House Republicans, however, opposed the spending measure, known as a continuing resolution, almost unanimously.

“While I’m sure President Trump will be only too delighted to have his last budget continue for almost a year after he left office, there is real work left to be done,” said Representative Tom Cole, Republican of Oklahoma and a member of the House Appropriations Committee. “Perhaps what is most frustrating has been the way in which the majority has bungled reaching a relatively simple deal on this particular continuing resolution.”

Across the Capitol, Senator Richard C. Shelby of Alabama, the top Republican on the Senate Appropriations Committee, said in a statement that he was “pleased that we have finally reached an agreement.”

But he offered a warning about the negotiations over the longer-term spending bills. He said that if Democrats continued to push for policies that Republicans oppose, such as lower levels of defense funding and the elimination of the Hyde Amendment, which blocks federal funding for abortions, “we’ll be having the same conversation in February.”

It remained unclear, however, whether other members of Mr. Shelby’s party would allow the short-term spending bill to advance in the Senate in time to avoid a shutdown this weekend. Senators Mike Lee of Utah and Roger Marshall of Kansas, both Republicans, led the push to cut off funding for the vaccine mandate.

“I don’t want to shut down the government,” Mr. Lee said in a floor speech. “The only thing I want to shut down is Congress funding enforcement of an immoral, unconstitutional vaccine mandate.”

Both senators said that they would allow the spending bill to advance only if their amendment could be subject to a simple majority vote, rather than one with a 60-vote threshold, which is needed to advance most major legislation in the Senate.

Given the 50-50 partisan split in the chamber, that would mean it would take only one Democrat joining Republicans in support of the proposal to pass it, and Senator Joe Manchin III, Democrat of West Virginia, suggested he had not ruled out doing so.

“I’ve been very supportive of a mandate for federal government, for military, for all the people that work on government payroll,” Mr. Manchin told reporters on Thursday morning. “I’ve been less enthused about it in the private sector.”

Mr. Manchin voted against a similar amendment in late September, just over a month before the Biden administration announced it would mandate that all companies with more than 100 employees require vaccination or weekly testing.

Several senior Republicans who have objected to the mandate have warned that the dispute is not worth a government shutdown, particularly as the nation confronts a new coronavirus variant.

The requirement, which the Biden administration had set to go into effect in January, has become ensnared in court challenges. In November, a federal appeals court kept a block on it in place and declared that the Occupational Safety and Health Administration had overstepped its authority in issuing the rule.

“I don’t think shutting down the government over this issue is going to get an outcome,” Senator Mitch McConnell of Kentucky, the minority leader, said on Fox News. “It would only create chaos and uncertainty, so I don’t think that’s the best vehicle to get this job done.”

But it would take only one senator lodging an objection to slow the spending bill’s passage and force a lapse in government funding.

“This is so silly, that we have people who are anti-science, anti-vaccination, saying they’re going to shut down government over that,” Speaker Nancy Pelosi, visibly exasperated, said at her weekly news conference. “We’re not going to go for their acts of anti-vaccine, OK?”

“So if you think that’s how we’re going to keep government open,” she added, “forget that.”