Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, has issued guidance to military commanders stressing that there will be no change in military policy toward transgender service members until Defense Secretary Jim Mattis receives further direction from the White House.

President Trump Wednesday announced via Twitter what appeared to be a reinstatement of the military's ban on transgender service members.

"I know there are questions about yesterday’s announcement on the transgender policy by the president," Dunford said in a written message to military commanders, according to a copy obtained by ABC News.

"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," the nation's top military commander continued.

"In the meantime, we will continue to treat all of our personnel with respect," Dunford said. "As importantly, given the current fight and the challenges we face, we will all remain focused on accomplishing our assigned missions."

The Pentagon was caught off guard by Trump’s Twitter announcement Wednesday that would reinstate the ban on transgender military service members that had been lifted by then-Defense Secretary Ash Carter last summer.

A Pentagon spokesman Wednesday referred questions to the White House.

After consultation with my Generals and military experts, please be advised that the United States Government will not accept or allow...... — Donald J. Trump (@realDonaldTrump) July 26, 2017

....Transgender individuals to serve in any capacity in the U.S. Military. Our military must be focused on decisive and overwhelming..... — Donald J. Trump (@realDonaldTrump) July 26, 2017

....victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail. Thank you — Donald J. Trump (@realDonaldTrump) July 26, 2017

Vice Admiral Robert Burke, the Navy's top personnel officer, issued guidance to his commanders Wednesday that no personnel actions should be taken until further guidance is received by the White House and no ongoing medical treatments for transgender sailors should be ceased.

"With regard to implications for those currently serving, OSD (Office of the Secretary of Defense) is working to quickly discern the President's intent," Burke said in a copy of the guidance obtained by ABC News. “Treating service members with dignity and respect is something we expect from our sailors at all times."

"Currently-serving TG Service members will continue to receive all necessary medical care," Burke wrote. "With regard to implications for those currently serving, OSD is working to quickly discern the President's intent."

The military does not track the number of transgender military service members through its personnel records, but the armed services do have information about service members who have contacted military medical services about a possible transgender transition.

About 160 sailors and fewer than five Marines are undergoing some form of transgender transition through the Navy's medical services, according to a Defense Department official. About 80 Army personnel are in similar transitions. The Air Force does not provide details about how many service members may be in transition.