The Navy plans to begin putting senior enlisted female sailors on submarines in December, officials announced on Friday.

The women will first be integrated onto ballistic missile submarines, which are larger than fast attack submarines, said Navy Cmdr. Renee Squier, head of the Office of Women's Policy for the Chief of Naval Personnel. 

The plan is to first integrate female senior enlisted sailors onto submarines, and then junior enlisted female sailors, she said. 

"The goal is to have each unit have 20 percent," Squier said, in order to build a "good ecosystem" for female submariners. 

The Navy first opened submarines to female Navy officers in 2012, and so far, more than 40 have served on them. But December will mark the first time enlisted female sailors will be allowed to do so. 

The changes will not begin until 90 days after the House and Senate Armed Services Committees of formally notified of the plan. That period must include 30 days of continuous session — likely to be in December, Squier said. 

So far, Congress has been "very cooperative" on integrating women in the service, she added.

Some have criticized allowing women to serve on submarines. They say sailors serve in close quarters on submarines. They warn that placing women on submarines among dozens of men could lead to incidents of sexual assault or pregnancy and possible negative health effects on women.

Squier, though, said there has been no major pushback from critics or lawmakers to the Navy's plans.

She said some modifications on submarines are being made to accommodate the enlisted women. Those would likely include creating separate bathrooms or sleeping quarters. 

There was a push under the Clinton administration to assign women to submarines, but the 2001 defense policy bill halted those efforts, according to a Congressional Research Service study.

Then-Defense Secretary Robert Gates notified Congress in 2010 of the decision to allow women to begin serving on submarines and in 2011, the Navy began to train women and female officers for submarines. 

The change is part of the Obama administration's push to open all currently closed military jobs to women, including in special operations. 

The four services are currently reviewing all closed jobs to see how to integrate women, and are required to submit to the Defense secretary any reasons why women may not be able to serve in particular jobs in 2016.

So far, the Marine Corps has been studying how to open infantry units to women, among other closed specialties, and the Army is currently accepting volunteers for Ranger School. 

Squier said there has not been a study on increased sexual assault on the submarines, but that Navy-wide, prevention awareness among sailors is increased. 

"I think that awareness has increased, I think our sailors feel they have leadership support," she said.