Top congressional negotiators in the early hours of Thursday unveiled the $1.2 trillion spending bill to fund the government through September, though it remained unclear whether Congress would be able to complete action on it in time to avert a brief partial government shutdown over the weekend.

Lawmakers are racing to pass the legislation before a Friday midnight deadline in order to prevent a lapse in funds for over half the government, including the Department of Homeland Security, the Pentagon and health agencies. They are already six months behind schedule because of lengthy negotiations to resolve funding and policy disputes.

Now that they have agreed on a final package, which wraps six spending bills together, passage could slip past 12:01 on Saturday morning because of a set of arcane congressional rules. House Republican leaders were signaling that they intended to hold a vote on the bill on Friday, bypassing a self-imposed rule requiring that lawmakers be given at least 72 hours to review legislation before it comes up for a vote.

There could be additional hurdles in the Senate, where any one lawmaker’s objection to speedy passage of legislation could prolong debate and delay a final vote.

Democrats and Republicans both highlighted victories in the painstakingly negotiated legislation. Republicans cited as victories funding for Border Patrol agents, additional detention beds run by Immigration and Customs Enforcement, and a provision cutting off aid to the main United Nations agency that provides aid to Palestinians. Democrats secured funding increases for federal child care and education programs, cancer and Alzheimer’s research.

“We had to work within difficult fiscal constraints — but this bipartisan compromise will keep our country moving forward,” said Senator Patty Murray, Democrat of Washington and the chairwoman of the Appropriations Committee.