Defense Secretary Ash Carter announced Thursday a new force-wide policy granting women 12 weeks maternity leave, a controversial move that will roll back some services recent efforts to expand that benefit to 18 weeks.

The change is a surprising rebuke to the Navy. Last year, Navy Secretary Ray Mabus expanded maternity leave for sailors and Marines to 18 weeks, a milestone change from the longstanding policy of 6 weeks leave for women who have children.

For the Army and the Air Force, the policy change effectively doubles the current policy that grants six weeks maternity leave. Yet both of those services had signaled public support for the Navy's move and were considering a similar change.

Carter's move creates a force-wide policy on a matter was for many years left up to the individual services.

"I concluded that twelve weeks of maternity leave across all of the force establishes the right balance between offering a highly competitive leave policy while also maintaining the readiness of our total force," Carter said at a press breifing Thursday.

"Twelve weeks is extremely generous ... it puts us in the very top tiers of American employers," Carter said.

The change is driven largely by concerns about retention. "Women at peak ages for starting a family leave the military at the highest rates," Carter said.

Carter added that the Navy and Marine Corps would honor the prior commitment to 18 weeks leave for women who are currently pregnant.

Mabus declined to comment directly on Carter's move to cut Department of the Navy's leave policy, but his spokesman said Mabus believes "meaningful maternity leave" is important for retention.

"Secretary Mabus has been clear since he announced 18 weeks of maternity leave for Sailors and Marines in July," said Capt. Patrick McNally in a statement to Navy Times. "He feels that meaningful maternity leave when it matters most is one of the best ways that we can support the women who serve our county and also serves as a safeguard against losing skilled service members."

Carter's move caused Air Force secretary James to back-pedal from statements she made in December, when she stated: "I am prepared to use my authority as secretary of the Air Force. I believe in what the Navy did, I think it was the right thing to do, and we're going to do the same thing. I'm here to tell you, it's coming."

Yet in a statement emailed to Air Force Times Thursday, James lauded Carter for his announcements, including the 12-week maternity leave, and called them "a positive step forward for our airmen and their families."

"This change places our Air Force in the top tier of organizations that offer 12 weeks maternity leave to new mothers," James said. "This is the right thing to do. This groundbreaking policy carefully balances our priority focus on mission effectiveness with ongoing efforts to attract and retain talent in a changing workforce."

The Army also said it was reviewing its leave policy in the wake of Mabus's move.

The new maternity leave policy was unveiled along with several other changes designed to make the military more family friendly.

Carter also announced a new force-wide policy for paternity leave, giving male service members 14 days of non-continuous time off after the birth or adoption of a child. That's up from the current policy that gives men 10 days paternity leave.

In another push to improve military life for women and mothers, Carter announced plans to create 3,600 new breast-feeding rooms across the country. The new policy will put a breast-feeding room in all military buildings that have more 50 female employees, he said.

"These rooms must be a designated, clean, and private space that is not a restroom. The room must also be equipped with electrical outlets, as well as table and chair access for each person using the room," Carter said.

The Defense Department will also expand access to child care on military installations by mandating that day care facilities extend service to a minimum of 14 hours each day.  The new rule will require the Child Development Centers to be open for a two-hour window on each end of an installation's workday.

All military services offer subsidized child care but families have complained for years military families about limited hours and lack of access.

Another change the Pentagon wants would grant some troops the duty station of their choice in exchange for a commitment to serve more time in the military. The Defense Department plans to ask Congress to change the current federal law that would grant commanders far more authority to use non-monetary incentives for obtaining extended service agreements.

"The services have been clamoring for this," said one defense official.

Stephen Losey contributed to this report.