Congressional leaders unveiled a $1.2tn spending package to fund much of the federal government on Thursday, with less than two days left to avert a partial shutdown.

Leaders of both parties celebrated the policy wins they notched in the negotiations over the bill, which will fund the departments of state, defense, homeland security and others through September.

In a statement hailing the legislation, the House speaker, Republican Mike Johnson, noted that the package would direct more resources to border patrol and rescind “another $6bn in unused Covid-era slush funds”. The immigration provisions include funding for 22,000 border patrol agents, marking the highest level ever, and an increase in Immigration and Customs Enforcement (Ice) detention capacity by more than 8,000 beds.

The bill will also cut off funding for the main UN relief agency that provides humanitarian aid to Palestinians in Gaza, a proposal endorsed by many Republicans, as the region faces widespread famine and other disease.

“Overall, during the FY24 appropriations process, House Republicans have achieved significant conservative policy wins, rejected extreme Democrat proposals, and imposed substantial cuts to wasteful agencies and programs while strengthening border security and national defense,” Johnson said.

Meanwhile, Democrats praised the bill’s investments in childcare and educational programs, saying they successfully prevented Republicans from slashing funding for many vital government services.

“We defeated outlandish cuts that would have been a gut punch for American families and our economy,” said Senator Patty Murray, the Democratic chair of the Senate appropriations committee. “And we fought off scores of extreme policies that would have restricted Americans’ fundamental freedoms, hurt consumers while giving giant corporations an unfair advantage, and turned back the clock on historic climate action.”

The House is expected to approve the package on Friday, leaving the Senate with just hours to pass the bill before the shutdown deadline at midnight. If the Senate does not pass the bill in time, about 70% of the federal government will shut down at 12.01am on Saturday.

Earlier this month, Congress passed a separate spending package that funded the rest of the federal government through the end of the fiscal year on 30 September. Once the second spending package is signed, it will eliminate any threat of a government shutdown until the new fiscal year begins in October.

Joe Biden has already indicated that he will sign the spending package “immediately” once it reaches his desk, but there are still some legislative hurdles remaining.

The House will consider the spending package under suspension of the rules, meaning Johnson will need the support of two-thirds of members to pass the bill. House Republican leaders typically prefer to give members 72 hours to read bills before holding a vote, but they appear ready to disregard that guideline in this case because of the shutdown deadline.

Johnson should be able to get the bill passed on Friday, but he is already facing pushback from some hard-right members of his conference, who complained that the legislation did not go far enough in restricting immigration.

On Monday, 43 House Republicans signed on to a letter urging members to oppose any spending package as a means of protesting Biden’s immigration policies.

“A vote to fund this government without policy reforms is a vote for these policies,” the Republicans wrote. “Therefore, we ask you to join us in rejecting the appropriations package (or anything similar) slated to be before the House that will directly fund these disastrous policies, and choose instead to stand against this assault on the American people and use the power given to us by our founders.”

Assuming the bill can pass the House, it will then move on to the Senate, where members will need to unanimously agree on an expedited timeline to pass the bill before Saturday. Some Republicans in the chamber, including Senator Rand Paul of Kentucky, have voiced discontent about fast-tracking the bill’s passage, so leaders will probably need to reach an agreement on an amendment schedule to get the legislation approved in time.

In a floor speech on Thursday, the Senate majority leader, Democrat Chuck Schumer, expressed optimism that a shutdown could be avoided.

“This funding agreement between the White House and congressional leaders is good news that comes in the nick of time,” Schumer said. “Once the House acts, the Senate will need bipartisan cooperation to pass it before Friday’s deadline and avoid a shutdown.”