WASHINGTON - The Senate remains in session overnight to advance legislation funding President Donald Trump's immigration enforcement agencies while Democrats and some Republicans seek to insert language that would permanently bar creation of a $1.776 billion settlement fund.

Republicans earlier rebuffed a Democratic bid to stop the fund, which aims to compensate the president's allies claiming political persecution. Yet Sen. Bill Cassidy of Louisiana signaled he would attempt once more to block the settlement during the extended session.

The proposed changes tested party cohesion and risked the immigration spending measure, given that several Republicans have consistently opposed the fund. The initial vote on the settlement stayed open roughly three hours while GOP senators weighed their positions.

"I feel optimistic that we will reach a conclusion," Senate Majority Leader John Thune, R-S.D., stated Thursday evening, though he conceded uncertainty over the final tally.

Thune has urged fellow Republicans for weeks to limit the bill to funding for Immigration and Customs Enforcement and Border Patrol, measures Democrats have stalled since early this year, and to avoid new provisions that might hinder passage.

Passage of an amendment restricting the settlement would create difficulties when the measure reaches the House, Thune noted, and could prompt a White House veto of the otherwise unifying immigration package.

The last time the Senate abruptly altered a Homeland Security funding package in March, the House declined to accept it and adjourned.

Trump's judgment fund, part of a settlement resolving his IRS lawsuit over leaked tax returns, has drawn criticism from numerous Republican senators.

Acting Attorney General Todd Blanche indicated this week that the fund would not proceed. Trump, however, expressed fresh doubts Wednesday afternoon after the Senate began debate on the immigration bill, telling reporters the settlement remains "very important" and that he does not know whether it is dead or paused.

"I would have to consult the lawyers," he added.

The Senate defeated a second amendment from Sen. Thom Tillis of North Carolina on Thursday that would have prohibited the settlement fund and redirected the money to a separate Justice Department anti-fraud account. Most Democrats opposed the measure, ensuring its failure, though more than 10 Republicans backed it.

Tillis argued the settlement fund, portions of which might reach Trump supporters involved in the Jan. 6, 2021, Capitol events, poses a political risk for the party.

"If Blanche indicates this is largely inoperative, why not codify that now?" Tillis asked. "Otherwise, members up for election face questions on this issue through Election Day, which serves no purpose given the DOJ position."

Additional amendment votes remained unclear.

Cassidy, who lost re-election last month after Trump backed his primary challenger, said he would still offer an amendment banning settlement payouts and might propose blocking a separate provision granting Trump and his family IRS audit immunity.

Several Republican senators expressed support but wanted to review final wording. Sen. John Cornyn, also defeated last month after Trump endorsed his opponent, agreed with the "thrust" but awaited details. Sen. John Curtis of Utah voiced similar caution.

Thune maintained the final bill should pass without settlement restrictions.

"This concerns border funding," Thune said. "It involves law enforcement, ICE and CBP. I am working to keep the focus on the central purpose."

Democrats offered further amendments overnight covering Trump's tariffs, tensions with Iran and immigration enforcement actions.

"Amendment after amendment, vote after vote, Republicans will answer to the American people," Senate Democratic leader Chuck Schumer said at the day's start.

Passage of the roughly $70 billion measure funding ICE and Border Patrol would conclude the Democratic blockade that sought policy changes following fatal shootings of two protesters by federal agents in January. The bill would finance the agencies for three years through the end of Trump's term.

Senate Republicans employ a complex procedural step to bypass the filibuster and enact the budget measure without Democratic support. Weeks of negotiations addressed various obstacles, including a scrapped $1 billion White House security request and backlash to the settlement fund.

Democrats insist any Homeland Security funding bill must include restraints on immigration authorities, such as improved officer identification and greater use of judicial warrants.

After federal agents shot Renee Good and Alex Pretti in Minneapolis, Trump accepted a Democratic request to separate the Homeland Security bill from a larger spending package. Bipartisan talks stalled, and department funding lapsed in mid-February without agreement on enforcement changes.

Congress later funded the remainder of the Homeland Security Department in late April with Democratic backing, yet ICE and Border Patrol stayed without regular appropriations.