WASHINGTON — Republican House lawmakers want Defense Secretary Jim Mattis to reverse military plans to allow transgender individuals to enlist in the military, and on Wednesday threatened legislative action if he moves ahead with the idea.

"This policy is not only costly, it's also a threat to readiness," said Rep. Vicky Hartzler, R-Mo., during debate on the annual defense authorization bill before the House Armed Services Committee on Wednesday.

"Military service is a privilege, not a right. It is predicated on the singular goal of winning the war and defeating the enemy. All decisions on personnel and funding should be made with this in mind."

Supporters of the new transgender policy insist that it does improve force readiness, by not restricting the talent pool of military recruits based on outdated stereotypes. But conservative lawmakers decried the rules, written by former President Barack Obama's Pentagon, amount to social engineering with little real benefit for the services.

Last week, officials from the Human Rights Campaign objected to reports that Mattis and senior Pentagon officials are considering a six-month delay in the new policy, scheduled to be implemented July 1.

Transgender troops are already allowed to serve openly, based on military changes implemented last year. But the new recruiting push now appears to face a significant delay while service officials grapple with questions about its implementation.

Hartzler and other opponents said it should be dumped completely. They promised action from the committee in coming weeks if Mattis does not halt the new order.

"This (policy) doesn't make (troops) more effective or efficient or deadly. What it does is distract everybody," said Rep. Duncan Hunter, R-Calif., who served with the Marine Corps in Iraq and Afghanistan.

"I couldn't imagine having to share showers with somebody that was a girl and didn't have a surgery to become a man but kept the girl stuff and now she's with a bunch of guys."

Democrats blasted those comments as inflammatory and ignorant. Rep. Chellie Pingree, D-Maine, noted the decision to change the policy came after "rigorous" department debate and study.

"The working group concluded that there would be minimal readiness impacts allowing the service members to serve openly," she said. "They signed off on an inclusive policy because they concluded on the basis of the research that inclusion wouldn't compromise readiness.

"Secretary (Mattis) indicated he will not revisit the decisions in positions in the previous administration absent concrete readiness at this point. We know of no such evidence."

No language regarding the policy was included in the final draft of the House authorization bill. But Hartzler said she was sidelining her objections "with the understanding and plea to the secretary to take the steps needed to restore readiness and make sure we do not waste precious taxpayer dollars" on the policy change.

"If that doesn’t happen, we need to take action on (this bill) once it gets to the House floor," she said.

Advocacy groups estimate that roughly 15,500 transgender service members are currently in the ranks. Defense officials are expected to announce an update on the policy in coming days.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.