WASHINGTON (AP) — Republican senators are considering dropping a proposal for $1 billion in security money for the White House complex and President Donald Trump's ballroom after it has failed to win enough party support on Capitol Hill.

Pressured by the White House, Republicans have tried to add the money to a roughly $70 billion bill to restore funding to U.S. Immigration and Customs Enforcement and the Border Patrol. But the security proposal has met with backlash from some GOP lawmakers who are questioning the cost and the lack of detail from the White House and U.S. Secret Service about how the taxpayer dollars would be used.

Sen. John Kennedy, R-La., said Wednesday that the bill was "back to square one" without the security money because "the votes are not there."

Sen. Thom Tillis, R-N.C., said the effort to add the security package to the bill was a "bad idea" and he does not think there is enough backing to pass it, even if it were reduced.

WATCH: What's in the billion-dollar paragraph behind the White House ballroom debate

The text of the bill has not yet been released. But Senate Majority Leader John Thune, R-S.D., acknowledged "ongoing vote issues" as leaders try to measure Republican support, as well as "ongoing parliamentarian issues" as they try to figure out what will be allowed in the bill under the chamber's rules.

WATCH: Trump calls planned White House ballroom 'a gift' to U.S.

The wrangling comes as Democrats have criticized Republicans for trying to fund Trump's ballroom when voters are concerned about basic affordability issues — and as some GOP lawmakers have grown increasingly frustrated with Trump. Several have spoken out against the administration's $1.776 billion settlement fund designed to compensate Trump's allies, and many were upset by the president's endorsement Tuesday of Texas Attorney General Ken Paxton in the party primary runoff next week against Sen. John Cornyn.

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"There's always a consequence with taking on United States senators," Thune said. Trump "obviously has his favorites and people he wants to endorse and that's his prerogative. But what we have to deal with up here is moving the agenda, and obviously that can become slightly more complicated."

Republican opposition blocks Secret Service request

Under the Secret Service request, about $220 million would pay for security improvements related to the ballroom. The rest would go for a new screening center for visitors, training and other security measures.

Tillis said the bill should not have included the other security improvements "because it's just giving everybody the 'billion-dollar ballroom.'"

"They need to explain to me why we need this," Tillis said, noting that Trump had originally said private money would cover the project.

Several other Republicans in the House and Senate have questioned the request, and senators left a briefing with the director of the Secret Service last week saying they needed a lot more information.

People "can't afford groceries and gasoline and healthcare, and we're going to do a billion dollars for a ballroom?" asked Louisiana Sen. Bill Cassidy, who lost reelection in the GOP primary on Saturday after Trump endorsed one of his opponents.

Sen. Jim Justice, R-W.Va., said he is supportive of the security money and thinks it is necessary to protect the president. But he acknowledged that the optics are not very good for Republicans, and that they have not communicated about it well.

"We've got people out there who are worried about how in the world they're going to have enough gas to get home," Justice said.

Tensions rise between Senate and White House

As Republicans challenged parts of his agenda, Trump unloaded on the Senate in a social media post.

He urged Republicans to fire the Senate parliamentarian, Elizabeth MacDonough, who said over the weekend that parts of the $1 billion security proposal cannot remain in the ICE and Border Patrol bill. Trump renewed his long-standing calls for the Senate to pass the SAVE Act, a Republican bill that would require all voters to prove U.S. citizenship, and to end the Senate filibuster.

"Republicans play a very soft game compared to the Dumocrats," he wrote. "It is their single biggest disadvantage in politics."

Trump said Democrats would eliminate the filibuster "on the First Day" if they ever get full power in Washington again and that Republicans need to "get smart and tough" or "you'll all be looking for a job much sooner than you thought possible!"

Republicans have been loyal to Trump on most issues, but they have resisted his repeated calls — even in his first term — to kill the filibuster, which triggers a 60-vote threshold in the Senate.

Hanging over the growing GOP rift is Trump's surprise endorsement of Paxton. That intervention has Republican senators privately fuming that it could cost them their majority in November as they view the incumbent, Cornyn, as the better candidate in the November general election.

Democrats test Republicans on settlement fund

As Republicans move forward on the immigration enforcement legislation, Senate Democratic leader Chuck Schumer of New York said Democrats plan to force a vote on Trump's proposed settlement fund.

Democrats have an opening because Republicans are trying to pass the immigration enforcement bill through a complicated budget process that requires a long series of amendment votes. Democrats are considering multiple amendments potentially to block that new fund outright or to ban any payments to Trump supporters who harmed law enforcement officers in the Jan. 6, 2021, attack on the Capitol.

Those amendments, along with others, could pass as a growing number of Republicans speak out against the fund and other parts of Trump's agenda.

Thune said he was "not a big fan" of the new fund, which the administration announced as a part of a settlement that resolves the president's lawsuit against the IRS over the leak of his tax returns. Cassidy called it a "slush fund" and said "you can't just make up things."

Tillis said he thinks it is a "real risk" that some of the rioters charged — and later pardoned by Trump — in the Jan. 6 attack could get compensation through the fund. He said that would be "absurd."

On Wednesday, two police officers who helped defend the Capitol in the 2021 assault sued to block the payouts. Acting Attorney General Todd Blanche, a personal attorney for Trump before joining the Department of Justice in Trump's second term, would not rule out the possibility that rioters who assaulted police on Jan. 6 would be eligible for compensation when he testified in a Senate hearing this week.