Washington — The prospects of the long-awaited border security deal negotiated in the Senate were quickly cast into doubt shortly after its release this week, with a large number of Republicans coming out against the legislation hours after it was unveiled. 

"I think the proposal is dead," Sen. Roger Wicker, a Mississippi Republican, told reporters after a meeting in Senate Minority Leader Mitch McConnell's office Monday night.

For others, the bill's prospects didn't appear as clean cut. Still, Senate Republicans emerging from a conference meeting late Monday expressed likelihood that the group would oppose a procedural vote on the bill set for Wednesday to give members more time to review the package, sparking questions about the bill's path forward as proponents look to hold onto momentum.

In remarks from the floor Tuesday morning, Senate Majority Leader Chuck Schumer pleaded with Senate Republicans to vote in favor of a procedural motion on Wednesday that would allow lawmakers to open debate on the issue. He warned that he would hold the chamber in session "as long as it takes" to consider the bill, and said lawmakers could offer amendments and ultimately oppose the bill if they wish.

"Let's vote. It's urgent," Schumer said. "We've spent months talking and debating. It's time to vote."

The Senate's border and foreign aid bill

Senate negotiators have for months been working on the agreement, which would mark the first comprehensive border security policy overhaul in decades and give the president far-reaching powers to clamp down on unlawful border crossings. On Sunday, the trio of senators released the text of the legislation, which is part of a larger supplemental funding package that also includes aid for Israel and Ukraine, along with humanitarian assistance in Gaza.

The deal's chances in Congress appeared to plummet after former President Donald Trump weighed in and told congressional Republicans to oppose the bill. Speaker Mike Johnson and House leadership have repeatedly said the bill is "dead on arrival" in the lower chamber, calling on President Biden to instead take executive action on the border. 

Sen. John Hoeven of North Dakota told reporters that the "sense of the room" on Monday night was that there wouldn't be support for a vote to move forward with debate on the bill Wednesday, saying that "people are still trying to understand the bill." The conference is expected to discuss the issue further at their lunch meeting on Tuesday.

Sen. John Thune, the No. 2 Senate Republican, said that "our members have a lot of questions about the substance" and are "still evaluating it."

"We'll live to debate another day tomorrow," Thune said. 

Even Sen. James Lankford, who negotiated the deal with Sens. Kyrsten Sinema and Chris Murphy, expected the procedural vote to open debate slated for Wednesday to fall short. Sixty votes would be needed to advance the legislation. 

"I would anticipate Wednesday, the cloture vote does not pass," Lankford said. "People are saying, 'Hey, I need a lot more time to be able to go through this.'"

Still, Lankford noted that there's a difference between opposing the bill flat-out and saying that the process can't be rushed, making clear that getting the deal passed remains a "work in progress."

"I'm not willing to do a funeral on it," Lankford said. 

Alejandro Alvarez and Alan He contributed reporting.

Kaia Hubbard

Kaia Hubbard is a politics reporter for CBS News Digital based in Washington, D.C.