WASHINGTON (Reuters) - The U.S. Congress, facing a Friday midnight deadline, toiled on Monday to finish writing a $1.2 trillion bill to fund the federal government through Sept. 30, as several thorny issues lingered, including funding President Donald Trump’s border wall.

A range of other hot-button initiatives was also slowing the unveiling of legislation that the Republican-controlled House of Representatives had aimed to make public late on Monday.

Republican lawmakers exiting a private meeting with House Speaker Paul Ryan said, for example, that there still was no decision on whether a couple of narrow, gun control-related measures could be inserted into the massive spending bill.

A Feb. 14 mass shooting at a high school in Parkland, Florida, has given impetus to a bill that would improve background checks for gun sales and another that would spend money to help schools defend themselves against gun violence but without putting new limits on weapons sales.

Republican Representative Mike Simpson, a senior member of the House Appropriations Committee, noted there was Republican opposition to the gun measures unless other steps such as expanding gun owners’ rights to carry concealed weapons across state lines were also enacted.

Simpson and other lawmakers said they did not know the fate of a move to include around $1.6 billion in funding for the border wall with Mexico, which is opposed by many Democrats and some Republicans.

“Everything that was significant is a work in progress. There is nothing defined” yet, said Republican Representative Mark Meadows, who heads the right-wing House Freedom Caucus.

Talks were expected to go late into the night.

Lawmakers were hoping to pass the “omnibus” spending bill before the start on Saturday of a two-week spring break. Doing so would put an end for six months to the possibility of any more government shutdowns by funding federal agencies for the rest of this fiscal year.

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

The federal government was forced to close over a weekend in January because of a similar budget battle.

POLARIZING MEASURES BEING SHELVED

With government funding running out at week’s end, several contentious items were tentatively being killed off to help speed passage of a bill that will significantly increase U.S. defense spending as well as many non-defense programs.

Several Republican lawmakers said a move had failed to renew federal subsidies to health insurers, which would help make “Obamacare” more affordable for low-income people.

Attempts to bolster the Affordable Care Act appeared to have collapsed after Republicans insisted on language that would have placed abortion prohibitions on those insurance plans and Democrats refused to go along.

“The speaker (Ryan) just said it wasn’t in there,” Meadows told reporters.

Trump discontinued the subsidy payments last year.

Trump also has threatened to veto the bill if it contains federal payments for constructing a New York-New Jersey railroad tunnel project known as the Gateway Program. Lawmakers said congressional leaders were still arguing over that money.

Three Republican House members told reporters that a separate initiative to impose an internet sales tax also appeared to be doomed.

Simpson, asked whether there were worries that the House and Senate would be unable to approve the spending bill before existing agency funds run out, said: “There’s always worries about that.”

Republican leaders were hoping to hold the House debate and votes on Wednesday, giving the Senate a couple more days to do the same before the Friday deadline. But the House timetable might have to be delayed a day, some aides and lawmakers said.