KINGS BAY NAVAL SUBMARINE BASE, Ga. -- The first U.S. women allowed to serve aboard submarines will be reporting for duty by 2012, the Navy said Thursday as the military ordered an end to one of its few remaining gender barriers.

The cramped quarters and scant privacy aboard submarines, combined with long tours of up to 90 days at sea, kept them off-limits to female sailors for 16 years after the Navy began allowing women to serve on all its surface ships in 1994.

There were some protests, particularly from wives of sub sailors, after the military began formulating a plan last fall. But it received no objections from Congress after Defense Secretary Robert Gates notified lawmakers in mid-February that the Navy intended to lift the ban. The deadline for Congress to intervene passed at midnight Wednesday.

Rear Adm. Barry Bruner, who led the Navy's task force on integrating women onto submarines, brushed aside questions about the potential for sexual misconduct or unexpected pregnancies.

"We're going to look back on this four or five years from now, shrug our shoulders and say, 'What was everybody worrying about?' " said Bruner, the top sub commander at Kings Bay Naval Submarine Base, where the announcement was made.

The first group of women will consist entirely of officers assigned to guided-missile attack submarines and ballistic-missile submarines, which have the most living space in the Navy's fleet. They'll be assigned to two subs based at Kings Bay and two others at the West Coast naval hub of Bangor, Wash.

Bruner said 24 women will be able to begin training for submarine officers, which takes at least 15 months, this summer. They'll be divided up so that three women are assigned to each sub's two rotating crews.

That grouping will let all three women aboard a sub share a single stateroom for sleeping. The single bathroom shared by a sub's 15 officers will be equipped with a sign to show if it's occupied by men or women.

Otherwise, most changes will likely be behavioral shifts by male sailors who aren't used to having women aboard, said Lt. Cmdr. Daniel Lombardo, executive officer of the submarine Alaska.

"The guys are probably used to walking to the restroom in their boxer shorts and stuff," Lombardo said. "But all in all, I think the adjustments for the crew are going to be minor."