WASHINGTON (NEXSTAR) — Momentum around a bipartisan federal gun safety bill may be wavering on Capitol Hill after lawmakers were unable to push forward the bill as planned this week.

Sen. John Cornyn of Texas, the top GOP negotiator who has faced some pushback from fellow Republicans this week, said he is starting to get a little concerned the two sides won’t get past some key differences.

On Thursday, Sen. Ted Cruz, R-Texas, said the bipartisan group of senators who brokered the deal had failed to introduce a real plan.

“We do not know what the specifics are,” said Cruz. “Details matter a great deal.”

The framework announced Sunday includes new mental health and school safety investments, anyone 21 and under would be required to undergo a more stringent review process before purchasing a gun and more money to help states adopt red flag laws.

Red flag laws allow family members to petition a judge to have the guns of someone deemed a danger temporarily removed.

Cruz and Sen. Josh Hawley call the red flag provision a deal-breaker.

“Bottom line on this is that I’ve got major problems with almost all of the red flag laws across the country,” said Hawley, R-Missouri.

Another sticking point remains closing the so-called “boyfriend loophole,” which bars domestic partners from purchasing guns if they have been convicted of abuse.

In the end, only 10 Republicans are needed to pass the plan in the Senate.

Lead Democratic negotiator Sen. Chris Murphy of Connecticut says he believes the two sides can agree on a text by next week.

On Thursday, Speaker of House Nancy Pelosi says the House is ready to pass the plan once the Senate finishes the bill.