The highest-ranking military officer in the country said that the military's transgender policy won't actively change until President Trump sends specific directions to the Pentagon.

"There will be no modifications to the current policy until the president's direction has been received by the secretary of defense and the secretary has issued implementation guidance," Joint Chiefs of Staff Chairman Gen. Joseph Dunford wrote in a letter.

The letter comes a day after Trump tweeted that he would ban transgender people from serving in the military.

On Wednesday morning, Trump wrote that "after consultation with my generals and military experts, please be advised that the United States government will not accept or allow transgender individuals to serve in any capacity in the U.S. Military.

"Our military must be focused on decisive and overwhelming victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail," Trump added. "Thank you."

The tweets prompted a swirl of questions about what would happen to currently serving transgender troops, questions for which neither the Pentagon nor the White House had answers on Wednesday.

Estimates on the number of transgender troops vary widely. On the high end, LGBT advocates put it at 15,000. On the low end, a 2016 RAND Corporation study estimated 2,450 individuals in active duty and 1,510 in the reserves.

About 250 troops have officially come out as transgender since the Obama administration lifted the ban on transgender troops in 2016.

Dunford's letter suggests those troops won't be immediately discharged.

In his letter, Dunford acknowledged that "there are questions about yesterday's announcement."

He stressed that "we will continue to treat all of our personnel with respect" while the military waits for further direction.

He also wrote that the issue should not distract the military from its warfighting mission.

"As importantly, given the current fight and the challenges we face," he wrote, "we will all remain focused on accomplishing our assigned missions."

A copy of Dunford's letter was posted online by CNN's Barbara Starr.

- This report was updated at 11:33 a.m.