CNN  — 

Senate negotiators are racing to finalize a deal on bipartisan gun legislation, but it’s not clear when they’ll be able to nail down an agreement, the latest sign of the challenge facing lawmakers as they attempt to find consensus on the highly polarizing issue.

Texas Sen. John Cornyn, the chief GOP negotiator on gun legislation, told CNN Thursday afternoon there’s no deal yet but expressed optimism and said talks are set to continue.

“We’re meeting again tomorrow and I hope to resolve remaining differences,” Cornyn said, noting the meeting would be virtual.

Sen. Chris Murphy of Connecticut, the lead Democrat in the negotiations, said of the effort, “We are not far away,” but added, “This is really hard stuff, politically and policy wise. We are not far away but we are not there yet.”

GOP Sen. Thom Tillis of North Carolina said he’s meeting with the group on Friday and that they are down to the “fine points.”

Lawmakers have been facing intense pressure to act in the wake of recent mass shootings in the United States, and at least 10 Republicans need to vote with Democrats in order to clear the 60-vote threshold to break a filibuster and pass legislation in the Senate.

Earlier in the day, Murphy told CNN he believes there will be more than 10 Republicans supporting gun safety measures in the Senate.

“I think we will put together a package that will get more than 10 Republican votes,” he told CNN’s John Berman on “New Day” Thursday.

Murphy said that he hoped the group could still reach agreement on a package by the end of the week.

“We’re still driving towards that goal,” he said. “This is complicated law, and we want to make sure that we get it right, not do it fast. So everybody is still at the table, nobody is walking away, and I’m still confident we have a path to get there.”

02:00 - Source: CNN
'What are we doing?!': Senator furious on floor over elementary school shooting

But hours after Murphy said he had hoped a deal would come this week, the top GOP negotiator poured cold water on those plans.

Cornyn told CNN “no,” he doesn’t expect a deal this week. “But having said that we’re making good progress,” he added.

Cornyn said that the legislation will likely be ready “by the end of this work period,” telling CNN, “in the next couple of weeks, I’m optimistic.”

On what’s being discussed, Murphy said federally mandated red flag laws are not on the table in discussions with Republicans. Those laws, which currently exist in 19 states, allow a judge to temporarily take away the guns of someone who is deemed a threat to themselves or others.

“I think there has been some lingering confusion,” Murphy said. “Past proposals have suggested a federal red flag law. I’ve actually never thought that was a good idea. I don’t think you want law enforcement to have to go into the federal courts to take, temporarily, firearms away from a dangerous individual. So we have to clean up some of the confusion around what we are proposing.”

He added: “We are talking about is incentivizing state red flag laws and providing substantial funding to implement them.”

He also said the group is “zeroing in” on the 18-21 age group on age limits or looking at juvenile criminal records for purchasing semiautomatic weapons.

“I think we continue to try to find a path to 60 votes that includes some provision that recognizes these 18- to 21-year-olds tend to be the mass shooters, and that many times they have juvenile criminal records or past histories of mental health that should prohibit them from buying a weapon,” he said.

He added: “So we are zeroing in on this population, trying to find the path to bipartisan agreement. I will say I think there’s Republican support for raising the age to 21. I don’t know whether there are 60 votes for that proposal, so we’re exploring some other important and impactful options.”

Utah Republican Sen. Mitt Romney told CNN on Thursday that he would support raising the age from 18 to 21 to buy a semi-automatic weapon such as an AR-15. He said he “hopes” it would be included in a final gun compromise.

“You have to be 21 to buy a handgun so saying you also have to be 21 to buy an assault rifle seems to make sense,” Romney said.

His comments come as Republicans largely seem opposed to the idea of raising the age from 18 to 21, but as CNN previously reported Senate Minority Leader Mitch McConnell has expressed an openness to the idea privately. The issue hasn’t been a serious part of the bipartisan gun talks.

Murphy continued to be very optimistic about the process of passing gun safety reform in the Senate, after telling CNN Sunday that he was “more confident than ever” lawmakers will be able to get something done to address gun violence across the US. Murphy also met with President Joe Biden earlier this week as the negotiations intensified on Capitol Hill.

“The urgency from the American public doesn’t seem to be going away,” Murphy said Thursday.

The House voted Wednesday 223-204 to pass a wide-ranging package of gun control legislation called the “Protecting Our Kids Act.” The measure is not expected to pass the Senate, however, amid widespread GOP opposition to stricter gun control.

Passage of the legislation in the House took place hours after an emotional hearing on gun violence in which families of victims pleaded for more action.

CNN’s Ted Barrett, Lauren Fox and Sonnet Swire contributed.