The remaining issue for Senate negotiators in trying to reach a deal on gun violence legislation this week is how big should background checks be for gun sales.

Two sources close to Senate negotiations told NBC News Tuesday that the issue is whether to increase waiting periods for youths purchasing firearms or to allow the FBI background checks on juvenile records.

This is a more narrow approach than previous legislation that sought to expand background checks. It includes a 10-year-old bill written by Sens. Joe Manchin (D-W.Va.) and Pat Toomey (R-Pa.) would have to conduct background checks at gun shows and online sales.

Senator John Cornyn (Republican from Texas), has been pitching his colleagues to the public about a proposal that would allow records of juveniles between 18 and 21 in the FBI’s National Instant Criminal Background Checks System.

The gunman who attacked Black shoppers in Buffalo, New York and killed 10 people was only 18 years old. Cornyn was also the shooter who shot and killed 19 children and 2 teachers at Robb Elementary School, Uvalde, Texas. Both were using AR-15-style rifles during the attacks.

Cornyn stated Tuesday that “I believe if this young man had been part the background check system nobody would have believed that he should purchase firearms.” He was able to pass the background check because he had not been 18 at the time he became 18.

The FBI does not normally make criminal or mental records available for purchase of firearms for adults. Cornyn is determined to change this and has been discussing it in detail with Sen. Chris Murphy (D-Conn.), his Democratic counterpart in talks. Thom Tillis (R-N.C.) and Kyrsten Sinema (D-Ariz.

Cornyn Murphy, Sinema and Murphy worked through their issues over a two-hour dinner meeting Monday evening. Negotiators hope to announce a deal before the end of this week, but talks could slip into next weeks.

Others in the bipartisan group don’t like the efforts to reduce background checks as part of the gun reform package.

Manchin and Toomey reached a bipartisan agreement to increase background checks in the wake of the Sandy Hook Elementary School massacre that left 26 people dead. The bill was defeated in the Senate by six votes due to opposition from the NRA.

Manchin stated Tuesday that he was from a gun-state and supports the Second Amendment. However, he said that for all of my law-abiding gunowners and gun friends with whom I shoot all the time and go hunting together… none of them felt it unreasonable to get a background check if selling their gun to someone they don’t know.

Toomey stated that he didn’t want to accept the premise that negotiators had abandoned the Toomey/Manchin bill.

Tillis said that he was on board the Cornyn Plan. He noted that approximately 45,000 juveniles are arrested each year for violent crimes, which is a number that does not usually appear in federal background checks.

Tillis stated, “It’s reasonable that we can look at those records to determine whether or not they were committed as an adult.”