Senate Republicans tangled on Tuesday over how far to push their border security priorities, with conservatives raising the idea of conditioning money for Ukraine on the United States meeting certain border security metrics, according to attendees of a conference lunch.

Negotiations linking immigration restrictions and foreign aid are mostly focused on policy changes that can earn bipartisan support, rather than restricting additional cash to Ukraine until the federal government meets certain migration metrics. The idea was rejected in those talks because a significant number of Republicans do not support that proposal, which could make it more difficult to get money to Ukraine in a timely fashion.

“I’ve been pushing for some forcing mechanism, though, like making Ukraine funding contingent on actually securing the border. That apparently was rejected,” said Sen. Ron Johnson (R-Wis.) after the meeting. “It would have had a lot of support in our conference.”

Oklahoma Sen. James Lankford, the lead Republican in those negotiations, argued adding that provision would cost GOP votes and divide the conference. He said it was not Senate Minority Leader Mitch McConnell’s idea to shelve the proposal, according to an attendee and a person briefed on the meeting.

Still, in the interview afterward, Johnson said McConnell had “apparently” rejected his idea and “made that decision for all of us.” Other conservative senators, including Sen. Rick Scott (R-Fla.), support that proposal.

How to enforce new border restrictions is one of the major sticking points in the negotiations and Republicans are divided over how far to go to get a deal with Democrats. Some conservatives will almost certainly oppose any agreement, arguing it wouldn’t go far enough to stop migrants from crossing the border. And Democrats are resisting changes to presidential parole authority, arguing it’s a crucial tool for the administration to manage the flow of migrants at the southern border.

Johnson said Republicans are also discussing a provision that would shut down the border when daily crossings exceed a certain number, though he questioned how enforceable such a policy would be. He said that making Ukraine’s money contingent on border crossing metrics is “about as good as we can do.”

“If you can get that. I mean, I’ll not only vote for it, I’ll promote the bill. I’m somewhat skeptical on Ukraine funding but sure, I want to support the freedom-loving people of Ukraine. I’d pay $60 billion to secure the border,” Johnson added.

Lankford and McConnell are trying to figure out what sort of compromise can draw not only significant Senate GOP votes but also support from House Republicans. As Sen. Kevin Cramer (R-N.D.) put it: “It doesn’t have to satisfy Ron Johnson, but it has to satisfy more Republicans.” He said he hoped 20 or 30 Senate Republicans will be able to endorse a deal.

Republicans say they won’t provide Ukraine with more funding without strict new border and immigration restrictions. That position created months of discussions led by Lankford and Sens. Kyrsten Sinema (I-Ariz.) and Sen. Chris Murphy (D-Conn.)

Senate Majority Leader Chuck Schumer told reporters Tuesday he’s been in contact with Murphy, Sinema and the administration as much as “five, six, seven times a day.” Murphy spoke alongside Schumer at Senate Democrats’ weekly press conference, telling reporters he briefed his colleagues on the “basics” of where negotiations stand.

But while Murphy and his fellow negotiators have largely shied away from detailing individual policy area disagreements in border talks, he specifically addressed presidential parole authority, which remains a major point of friction.

“We are not interested in taking away from the administration tools they use today to help better manage the border,” Murphy said. “And so when we talk about this topic of parole, it is very important to understand that it is used today as a way that the administration is able to better manage the flow” of migrants.

Murphy did not forecast an immediate resolution to hold ups — but said “we are where we are” and that negotiators are “trying our best to get an agreement that gives the administration new tools to be able to better manage the border while living up to basic fundamental American values.”

Anthony Adragna contributed to this report.