House Republican leaders’ plan to hold a vote on a gun-control proposal this week is on hold amid objections from conservatives concerned with the legislation and a broader package of counterterrorism measures.

GOP leaders announced late last week that they would hold a vote as soon as Wednesday on legislation that, among other provisions, would prevent suspected terrorists from purchasing firearms if the government can prove within three business days that there is probable cause to believe an individual has terrorist ties or sympathies.

But GOP leaders are now encountering resistance from some Republican members, particularly conservatives.

Following a conference meeting Wednesday morning, House Speaker Paul D. Ryan (R-Wis.) said GOP leaders “want to make sure that we codify a practice of making sure that terrorists don’t get guns while preserving citizens’ rights” to purchase firearms. He said he believes a balance can be struck between the two concerns.

“We can have security and keep to the Constitution at the same time,” Ryan said.

He would not commit to a schedule for bringing up the bill.

“The last thing we’re going to do is rush something to the floor that we don’t have right,” Ryan said.

Democrats oppose the GOP package as they push stricter gun restrictions following the recent mass shooting in Orlando.

Republican members emerging from the meeting said there is no clear consensus on how to move forward.

Conservative members said they could not support the legislation in its current form due to concerns over whether it does enough to protect the rights of gun owners and because they have questions about the legislation’s counterterrorism provisions. Meanwhile, some moderate members said they favor a more aggressive approach to restricting the sales of firearms to suspected terrorists.

“We’re going to whip it,” Rep. Ryan Zinke (R-Mont.) said. “I don’t think the Democrats are going to get behind it, so this is going to be whether we can get enough votes on the Republican side to pass it.”

The House Freedom Caucus, a group of about 40 hard-line conservatives, said its members would not support the bill unless they could make changes to it, although caucus co-founder Matt Salmon (R-Ariz.) said they do not yet have a specific list of amendments they want to receive a vote.

Salmon said Ryan told GOP members Wednesday morning “that there are members that need to have this vote” on the counterterrorism package, a likely nod to the tough re-election races in swing districts where there is support for some restrictions on gun sales following the recent mass shootings.

Salmon said his chief objection is that the bill wasn’t moved through the committee process where rank-and-file lawmakers would have had a chance to put their mark on the proposal. Several other members are concerned the legislation would not give individuals enough legal recourse to challenge their inclusion on a terrorist watch list and that it would give expanded powers to the Justice and Homeland Security departments.

“I’ve still got major reservations,” said Rep. Dave Brat (R-Va.), a Freedom Caucus member. He said leaders are “just kind of putting bills together that are talking-point, bullet-point oriented, that don’t have substance” and are “messaging gimmicks.”

Brat said the homeland security provisions were “even more of a disaster in my view” than the gun control provision and without changes, he would likely vote no on the bill and doubted it would pass.

Pointing to his lack of trust in current administration officials, Brat said his main concern is that the policy proposals rely on the attorney general to maintain lists of suspected terrorists and would create a new counterterrorism office within the Department of Homeland Security.

If Attorney General Loretta Lynch “is still going to be in charge of who’s on the list, that’s a problem,” he said. Brat added that Homeland Security Secretary Jeh Johnson is too “involved in the unconstitutional amnesty” plan to shield illegal immigrants from deportation – a program a deadlocked Supreme Court effectively blocked last month — to be trusted with more responsibility.

But while the guns measure and the counterterrorism package appears stalled, the House voted 422 to 2 on Wednesday to pass a comprehensive mental health bill written by Rep. Tim Murphy (R-Pa.), a clinical psychologist. He began drafting the legislation to overhaul the federal system for identifying and treating mental health cases in the wake of the 2012 shooting at the Sandy Hook elementary school in Newtown, Conn.

Murphy has insisted his mental health legislation is not a guns bill, but GOP leaders have long considered it an integral part of a national response to mass shootings.

“This is bipartisan reform,” Ryan said, adding that “the issue of mental illness” was “something that we think needs to be addressed, to address the gun violence that is occurring in America.”

Though Democrats voted for the measure, they raised concerns it would not have the desired impact if Congress did not put more money behind the programs.

“It is a hollow promise if there’s no some money in it,” said Rep. Jim McDermott (D-Wash.) “To think that state legislatures or somebody is going to find the money somewhere is simply not real.”

Meanwhile, House Democrats continue to push for votes on two gun-control measures they highlighted last month during a 26-hour sit-in on the House floor. One proposal would expand background checks and the other would prevent suspected terrorists from purchasing a gun without the time limitations in the Republican-backed measure.

Many House Republicans oppose giving Democrats votes on the bills for fear it could be seen as rewarding the protest.

Ryan and House Majority Leader Kevin McCarthy (R-Calif.) are expected to meet Wednesday with the Sergeant-At-Arms Paul D. Irving to determine whether they can conduct a formal investigation into the sit-in to determine if any House rules were broken, with the potential of censuring or otherwise punishing Democrats for the protest.

Several members complained that Democrats broke chamber rules during the protest, which they live-streamed, and that they raised campaign funds off it as well. Rep. Ann Wagner (R-Mo.) said that the Office of Congressional Ethics and the House Parliamentarian would also look into the matter.

“I do believe there need to be repercussions,” Wagner said. “I think we’re exploring a lot of different options in that regard.”

Some of the options House Republicans discussed Wednesday included revoking staff floor privileges for the members who brought their aides onto the floor against House rules, according to Rep. Louie Gohmert (R-Texas).

“There’s all kinds of powers the Speaker has if he wants to use them,” Gohmert said.

They also discussed setting up penalties so that in the future the consequences of breaking rules are clear.

“One of the ideas that came out is like the NFL or the NBA – when their players commit violations, they get fined,” Salmon said, noting it would be difficult to apply punishments retroactively. “That’s something I think we should consider for the future.”

Democrats did not resume their sit-in this week, but several dozen of them gathered with survivors and relatives of victims of gun violence on the steps of the Capitol Wednesday to campaign for votes on their two gun control measures.

There are a small number Republicans who would like to see votes on more expansive gun-control measures than what leadership is proposing.

Rep. Bob Dold (R-Ill.) said he is hoping for a vote on a bill he co-sponsored that would prevent anyone on the FBI’s No Fly or Selectee Lists from purchasing a firearm. The bill is identical to compromise legislation the Senate voted on last month.

“Certainly that’s what we’re pushing for,” Dold said.

And even some GOP members who aren’t pushing for specific amendments are concerned their party’s gun-control proposal might be too thin.

Rep. Mark Sanford (R-S.C.) suggested it might be difficult for him to support a bill that didn’t give the government more time to close the so-called “Charleston loophole” – a reference to rules that allow licensed firearms dealers to complete a sale if a background check isn’t completed within a three-day waiting period.

That provision has been hotly debated in the wake of the 2015 shooting at a church in Charleston, where a processing mistake led to the shooter being sold a gun he should not have been able to buy.

“If all the burden of proof is still on law enforcement and there’s no longer pause, some people back at home still have questions about that,” Sanford said.