WASHINGTON — Congressional leaders said Tuesday morning that they had reached an agreement on the final package of spending legislation to fund the federal government through the fall, though it was unclear whether they would be able to pass it in time to avert a brief partial shutdown over the weekend.

House Republicans, Senate Democrats and the White House had been at loggerheads over funding levels for the Department of Homeland Security. For days, they had been litigating disagreements that threatened to imperil the spending package that also funds the Pentagon, the State Department and other agencies. They are facing a midnight Friday deadline to pass the measure and avert a lapse in funding.

A breakthrough Monday night, in which Democrats and Republicans were able to agree to homeland security funding levels for the rest of the fiscal year, allowed negotiators to finalize their deal.

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“An agreement has been reached” that will enable Congress to fund the government through Sept. 30, House Speaker Mike Johnson said in a statement. “House and Senate committees have begun drafting bill text to be prepared for release and consideration by the full House and Senate as soon as possible.”

Even as the measure was being written Tuesday, President Joe Biden issued a statement saying he planned to “sign it immediately.” No details were immediately available of a package expected to total about $1 trillion.

Still, the delay in striking the deal could pave the way for a brief lapse in government funding over the weekend. It will take congressional staff time to draw up the text of the bill, which wraps six spending measures into a sizable piece of legislation.

House Republicans have demanded that Johnson abide by an internal rule that allows lawmakers 72 hours to consider the text of a bill before they vote on it, though previous House leaders have at times abandoned that guidance.

And any number of senators may create procedural hurdles for the bill’s passage and demand votes on proposed changes or object to its quick consideration. Those tactics could push final passage past 12:01 a.m. Saturday, when funding is set to expire.

“Making headway depends on serious cooperation,” Sen. Mitch McConnell, R-Ky., the minority leader, said Tuesday.

“Providing for the common defense is among our most basic constitutional responsibilities, and we need to be honest with ourselves,” McConnell said. “Growing threats and increasing military requirements make fulfilling this responsibility even more critical. The legislation in front of us will not be Congress’ last word, but it represents an important down payment.”

Late last year, Johnson chopped the spending process in half, creating two partial government shutdown deadlines instead of one, in an effort to avoid asking members to take a single vote on a huge catchall to fund the entire government, which Republicans have objected to repeatedly.

Lawmakers negotiated and passed a six-bill, $460 billion spending package that just barely met the first deadline March 8, and are now repeating the process — this time haggling over funding for more politically fraught agencies — before the second deadline at the end of this week.

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