White House spokesperson Sarah Huckabee Sanders pointed to upcoming guidance on whether transgender troops can stay in the armed forces. (Screenshot via CSPAN)

White House Press Secretary Sarah Huckabee Sanders expressed uncertainty on Wednesday when asked whether transgender people currently serving in the armed forces will be able to remain under President Trump’s new ban on their service.

Under questioning from ABC News’ Jonathan Karl, Sanders was unable to say whether the estimated 15,000 transgender troops currently in service will be thrown out of the military.

“That’s something that the Department of Defense and the White House will have to work together as implementation takes place as it is done so lawfully,” Sanders said.

Pressed further on whether transgender troops currently in service, such as those serving in Afghanistan, will be sent home, Sanders repeated her non-answer.

“Again, the implementation of policy is going to be something that the White House and the Department of Defense have to work together to lawfully determine,” Sanders said. “I would imagine the Department of Defense will be the lead on that and keep you posted as that takes place.”

Asked about the timeline for upcoming guidance, Sanders said, “We’ll let you know when we have an announcement.”

Sanders insisted Trump’s decision to ban transgender people from the armed forces was a “military decision,” deriding it as an “Obama policy.”

“He’s also voiced that this is very expensive and disruptive policy and based on consultation that he’s had with his national security team, came to the conclusion that it erodes military readiness and unit cohesion and made the decision based on that,” Sanders said.

It’s hard to say why transgender service would be either costly or disruptive. Former Defense Secretary Ashton Carter implemented it last year after a year-long review. Military experts have said the costs of transition-related care in the armed forces would be negligible.

In the aftermath of Trump announcing on Twitter Wednesday morning the U.S. military “will not accept or allow” transgender people, questioning on the transgender military ban made up a significant portion of the White House briefing.

The questioning seemed at one point to rile Sanders, who’s newly minted as White House press secretary following the resignation of Sean Spicer. Sanders threatened to shut down the briefing if inquiries on the subject continued.

“Guys, I really don’t have anything else to add on that topic,” Sanders said. “As I do, I’ll keep you posted, but if those are the only questions we have, I’m going to call it a day, but we have question on other topics, I’ll be happy to take them.”

Other questions during the briefing focused on whether Trump, who once said he’d be better on LGBT issues than Hillary Clinton, has betrayed his campaign promises to the LGBT community.

In one exchange between Sanders and NBC News’ Peter Alexander, who pointed out Trump told LGBT people “I will fight for you” during his presidential campaign, Sanders insisted Trump continues to support everyone despite his ban on transgender military service.

“I think the president had made very clear he’s committed to fighting for all Americans,” Sanders said.

Although observers have speculated Defense Secretary James Mattis was kept in the dark on the new policy based on his ongoing six-month review of transgender military service, Sanders said he was advised of Trump’s plan Tuesday night before the president announced it on Wednesday.

“When the president made the decision yesterday, the secretary of defense was immediately informed as were the rest of the national security team,” Sanders said.

When one reporter identified other countries with transgender military service and questioned if Trump had looked to them, Sanders said her responsibility is to speak for the U.S. government.

“I can’t speak to anything about another country,” Sanders said. “I’m pretty focused on making sure we get good things happening here.”

A shouted question from the Washington Blade at the end of briefing on whether Vice President Mike Pence advised Trump to reinstate the transgender military ban went unanswered.