"This Congress is moving very quickly," he said. "There's a crowded agenda on the Senate floor and if we don't do something soon, we will lose a historic moment where we really should rise (to) the moment and make the reforms necessary."
While the lead negotiators released a statement last week announcing they've "reached an agreement framework," several sources have told ABC News that behind closed doors there are still major points of contention.
What's putting the deal at risk?
The latest hurdle is an emerging divide within police unions, which are closely involved in the negotiations.
The discussions have dragged on for months, already blowing past two self-imposed deadlines. As talks progressed, lawmakers turned to outside groups for insight -- holding a meeting with two police unions, the Fraternal Order of Police and the International Association of Chiefs of Police in late May.
At the time, Republican Sen. Tim Scott of South Carolina told Booker that if he could get the unions "on board with a proposal, he would not stand in the way," a source familiar with the discussion told ABC News.
Booker floated a potential compromise to the unions, gaining their initial support, according to two sources familiar.
But when other unions caught wind of the floated proposal, they fired back.
The National Association of Police Organization encouraged the other negotiators to reject it. In a June newsletter, NAPO said, "Sen. Booker froze out NAPO and other police groups, despite the fact that NAPO represents just about all law enforcement officers in the senator's state of New Jersey."
According to sources familiar, Booker's proposed measure tried to strike a balance of providing more resources to police departments but also giving the federal government more power to bring cases against officers who committed acts of misconduct in four areas: excessive force, sexual misconduct, theft and obstruction of justice. It did not touch qualified immunity, a sticking point for Republicans and a red line for many progressive Democrats.
Rep. Karen Bass, D-Calif., said that she fears the infighting could put the entire deal at risk.
"Absolutely I worry that it could prevent us from coming to a deal. And you know what? I think that it would be a really sad statement about the profession," Bass said on Tuesday.
Booker said Wednesday that his meeting with the Fraternal Order of Police executive Jim Pasco made him more hopeful for police reform legislation to gain bipartisan support in the Senate.
"I told a great guy named Jim Pasco I viewed him as like an ogre before I got there, because these guys are tough, tough union and have not shown -- in my opinion -- the level of desire for reform. But Jim and I -- along with other law enforcement agencies -- had three weeks in negotiation, working up a lot of respect for him, as I've always had respect for his membership, we came to some accord," Booker said. "And if we can -- a Democrat from New Jersey and the administrative head of FOP -- come to a lot of agreements, I'm sure hoping that Tim and I can work the final details out and get a bill done."
"One of the reasons why a lot of law enforcement groups I've been negotiating with have leaned in is because they just know we are losing ground because of the erosion of trust amongst communities and law enforcement," he added.
With slim margins on both sides of the aisle in Congress, Booker said there's a "50-50 chance whether we get something done or not. If we don't act, this is another shameful moment for Congress, and I know I'm at the center of that. And that's why I've been bending and contorting myself in every way to try to make a bill that can attract people on both sides of the aisle."
Tensions run high
As details of the negotiations trickled out, the backlash was swift.
Publicly, Graham slammed the proposal.
"There ain't no way in hell that's going anywhere," Graham said. "The conversations we had about police reform were completely different than the document that was produced."
Graham's public comments caught Democrats off guard, according to two sources who believed Booker followed through on a request from Scott and did "the impossible" by getting the support of two large police unions. Republicans accused Booker of acting alone.
The NAACP, which has also been closely involved in negotiations, is growing increasingly frustrated and sounding the alarm about the role police unions are playing in the talks.
"Many in law enforcement agree that meaningful change is necessary, but unfortunately, a few are committed to standing in the way with a goal of obstructing the process. Police unions and partisan politicians should not control and dilute the terms of the police reform bill, nor delay any of its progress," NAACP President Derrick Johnson said in a statement. "This bill must be for the people."
This week, eight civil rights organizations including the NAACP, The Urban League and the National Action Network, took a direct jab at police unions accusing them of obstructing the negotiations.
The National Sheriffs' Association pushed back on any accusations that they are trying to sink the bill.
"That's not true at all. We're supportive of the process and we've been completely transparent with the things that we agree and disagree with -- with the senators," an official with the group told ABC News.
"To say that law enforcement is trying to delete the bill or they don't want this, it's just not a fair assessment," the official said, emphasizing that their role is to advocate on behalf of sheriffs.
The Fraternal Order of Police, who backed Booker's initial proposal came out with a statement on Wednesday underscoring that talks are on the brink.
"Given the politics of the moment, we seem to be poised to undo more than a year's worth of work toward common sense criminal justice reform," said Patrick Yoes, the group's president, in a statement. "Demagoguery and scare tactics have jeopardized the future of these efforts and may well have derailed the negotiations."
All sides ask: What now?
Lawmakers have been under increased pressure in recent weeks, having missed the first deadline to pass the bill into law by the first anniversary of Floyd's death. One source told ABC News that members of the NBA have held multiple bipartisan meetings with lawmakers to push the bill, with several more meetings planned with lawmakers on both sides of the aisle. In May, James Cadogan, the executive director of the National Basketball Social Justice Coalition said in a statement that the league is "calling on our elected representatives of both parties to work together to pass the George Floyd Justice in Policing Act in the U.S. Senate now and present it to President Biden for him to sign into law this year."
Two sources close to the talks also told ABC News that there is growing concern about how the upcoming midterm elections will affect the negotiations with some fearing Republicans may be less willing to strike a deal, as their party pushes a law-and-order message.
One source close to ongoing talks told ABC News, "a compromise isn't me walking over to you, it's us meeting halfway and that's not what's happening at this point."
"The goal posts keep moving," the source continued.
Scott's office declined to comment.
"The process -- finalizing the bill is difficult," one source familiar with Scott's thinking said. "Despite the challenges, we are going to continue to move forward with the negotiation process, ironing out specifics within the broader, agreed-upon framework," the source added.
"(Sen. Scott) is committed to making sure any final bill honors the family of Walter Scott, George Floyd and any family that has been affected, while at the same time providing the resources officers need to keep our communities safe."
Still, no one appears ready to walk away from the negotiations and White House press secretary Jen Psaki said recently that "the president remains eager to sign the police reform bill into law."
ABC News' Sydnie Cobb contributed to this report.