WASHINGTON — Rep. Lee Zeldin’s measure to require law enforcement to get court orders to stop suspected terrorists from buying guns — a key part of the House Republicans’ anti-terrorism package — has run into opposition from the right-leaning bloc of his own party.

Republican leaders delayed a vote that had been expected Wednesday on the legislation they crafted in response to Isis-inspired mass shootings in Orlando and San Bernardino, following pressure by Democrats’ rare sit-in demanding votes on their two gun bills.

House Speaker Paul Ryan (R-Wis.) acknowledged the disagreement within his party over the legislation but said he still planned to bring it to the floor before Congress breaks at the end of next week until September.

“We have members from both sides of the aisle who want to make improvements, who want to make changes to the bill,” Ryan said at a news conference. “The last thing we’re going to do is rush something to the floor that we don’t have right.”

At the news conference, Zeldin (R-Shirley) urged lawmakers to back his NRA-supported measure. The bill would stop a gun sale to a suspected terrorist after law enforcement obtained a court order based on probable cause within three working days of the attempted purchase.

But the House Freedom Caucus, a bloc of about three dozen conservatives, said Wednesday it opposes the package “for failing to do enough to address the threat of radical Islamic terrorism and because of the inclusion of gun control provisions that fail to adequately protect due process.”

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Caucus member Rep. Justin Amash (R-Mich.) charged in a blog post that Zeldin’s measure would “grant the government power to target law-abiding Americans” through the authority to ban gun sales to people who haven’t been charged or convicted of criminal or terrorist activities.

The caucus also complained that the package was created in a closed process that did not include ideas for improvement from members, according to Darin Miller, spokesman for Rep. Jim Jordan (R-Ohio), the caucus chairman.

Zeldin defended his measure by saying it “in no way, shape or form infringes upon the rights of law-abiding gun owners. What it does is ensure that terrorists do not have the ability to legally purchase firearms.”

He said he has no problem with giving lawmakers time to comment. Zeldin said Wednesday afternoon that the package still might get a vote this week.

Also Wednesday, House Minority Leader Nancy Pelosi (D-Calif.) and other Democrats stood on the Capitol steps with family members of gunshot victims to continue to press for House action on their bills.

Democrats back a bill sponsored by Rep. Peter King (R-Seaford) and opposed by the NRA that does not require law enforcement to show probable cause and get a court order to prevent someone on a terrorist watch list from buying a firearm.