WASHINGTON — Saying it’s the right thing to do, Defense Secretary Ash Carter announced Thursday that transgender people will be allowed to serve openly in the U.S. military, ending one of the last bans on service in the armed forces.

“Americans who want to serve and can meet our standards should be afforded the opportunity to compete to do so,” said Carter, laying out a one-year plan to implement the change.

Under the new policy, by Oct. 1, transgender troops already serving should be able to receive medical care and begin formally changing their gender identifications in the Pentagon’s personnel system.

And, a year from now, the military will begin allowing transgender individuals to enlist, as long as they meet standards and have been stable in their identified genders for 18 months.

Carter’s announcement comes despite concerns from senior military leaders that the department is moving too fast and that more time is needed to work through the changes.

According to defense officials, the military leaders, including Gen. Mark Milley, the Army chief of staff, and Gen. Robert Neller, commandant of the Marine Corps, said that while they aren’t opposed to lifting the ban, they thought the new rules didn’t include enough specifics.

Carter said he discussed the plans extensively with his military leaders and that, based on their recommendations, he made adjustments to the timeline. He said he has been told that the services now support the timeline.

According to Carter, a study by the RAND think tank found that there are between 2,500 and 7,000 transgender service members in the active duty military, and another 1,500 to 4,000 in the reserves.