WASHINGTON (Reuters) - The U.S. Congress, facing yet another government shutdown deadline at midnight on Friday, will try this week to approve a massive spending bill that would end lawmakers’ nettlesome budget infighting, at least through Sept. 30.

FILE PHOTO: People walk by the U.S. Capitol building in Washington, U.S., February 8, 2018. REUTERS/Leah Millis/File Photo

Republican leaders in the House of Representatives hope to unveil soon the product of long negotiations over a $1 trillion spending bill. It would fund all of the federal government’s activities, except for the gigantic “mandatory entitlement” programs such as Social Security and Medicare, which do not have to be renewed annually.

The Republican-controlled Congress was supposed to have completed this work by Sept. 30, 2017, the start of fiscal 2018, but it has not done that. Instead, the government has been running on a series of short-term, stopgap funding measures.

As of Sunday, negotiators were still trying to put the finishing touches on a longer-term bill. Its progress has been slowed by partisan flashpoints between Republicans and Democrats, including immigration policy.

Failure to pass this major spending bill by the end of Friday would leave Congress with two options: force federal agencies to suspend operations ranging from national park lands to medical research due to a lack of funds; or pass another in a series of stopgap bills.

In January, Washington was plunged into partial shutdown mode for a weekend because of disagreements on a stopgap bill.

Some conservative Republicans are likely to vote against the major bill, which could push budget deficits for fiscal 2018 to more than $800 billion. That would give Democrats leverage to make demands to win their votes needed for passage.

Democrats are resisting President Donald Trump’s call for money to start building a wall on the U.S.-Mexico border and to hire more immigration enforcement agents.

Republicans want to insert gun-related measures, including one to provide new grants for school safety programs and one to tighten background checks on gun purchases. Both fall far short of what gun control advocates want.

Republicans regularly push for anti-abortion initiatives in spending bills, and this year’s is no different.

Negotiators were also seeking to fund new infrastructure projects. There also was a fight underway over the costly New York-to-New Jersey “Gateway Program” railroad tunnel project, which Trump opposes.

If Congress does manage to pass its “omnibus” spending bill by Friday, that would not end budget infighting for good.

Lawmakers would then have until Sept. 30 to pass a dozen separate spending bills for fiscal 2019, which begins on Oct. 1, or resume their game of blaming each other for possibly causing shutdowns.