SAN FRANCISCO -- Four female service members filed a lawsuit Tuesday challenging thePentagon's ban on women serving in combat, hoping the move will addpressure to drop the policy just as officials are gauging the effectthat lifting the prohibition will have on morale.

The lawsuit, filed in federal court in San Francisco, is the secondone this year over the 1994 rule that bars women from being assigned toground combat units, which are smaller and considered more dangeroussince they are often in battle for longer periods.

The legal effort comes less than a year after the ban on gays servingopenly was lifted and as officials are surveying Marines about whetherwomen would be a distraction in ground combat units.

"I'm trying to get rid of the ban with a sharp poke," said U.S. ArmyStaff Sgt. Jennifer Hunt, who was among the plaintiffs in the latestlawsuit and was injured in 2007 when her Humvee ran over an improvisedexplosive device in Iraq.

Hunt and the other three women said the policy unfairly blocks themfrom promotions and other advancements open to men in combat. Three ofthe women are in the reserves. A fourth, Marine Corp Lt. ColleenFarrell, leaves active duty this week.

Women comprise 14 percent of the 1.4 million active militarypersonnel. The lawsuit alleges that women are barred from 238,000positions across the Armed Forces.

At a Washington, D.C., news conference, Pentagon press secretaryGeorge Little said the Defense Department was making strides in allowingmore women into combat. He said Defense Secretary Leon Panetta hasopened about 14,500 combat positions to women.

"And he has directed the services to explore the possibility ofopening additional roles for women in the military," Little said. "Hisrecord is very strong on this issue."

American Civil Liberties Union Ariela Migdal, who represents the fourwomen, said Panetta's actions weren't enough. She called for an end tothe combat ban. "These tweaks and minor changes on the margins do adisservice to all the women who serve," she said.

"It falls short," she said. "It is not enough."

Marine Corps Capt. Zoe Bedell said she left active duty, in largepart, because of the combat exclusion policy. Bedell said she wasfrustrated that her advancement in the Marines was blocked by herinability to serve directly in combat units.

"The military is the last place where you are allowed to be discriminated against because of you gender," she said.

Bedell said the blurred front lines of modern warfare, with suicidebombs and sniper attacks, have put more and more women in combatsituations.

More than 144 female troops have been killed and more than 860 havebeen wounded in Iraq and Afghanistan since the wars began, according toPentagon statistics.

Military leaders say they want to make sure lifting gender-basedbarriers would not disrupt the cohesion of the smaller combat groundunits and military operations.

The Marine Corps' top leader, Gen. James Amos, ordered a survey of53,000 troops to get their views, including whether they believe womenin those units would distract male Marines from doing their jobs. Theresults have not been released yet.

The lawsuit alleges the ban violates constitutional female servicemembers' equal rights. "As a direct result of this policy," the lawsuitstates, "women as a class and solely because of their gender arebarred from entire career fields.

The lawsuit also alleges that women are already serving unofficially in combat units.

Air National Guard Major Mary Jennings Hegar sustained shrapnelwounds in 2009 when she exchanged fire on the ground in Afghanistanafter her Medevac helicopter was shot down. Both she and Hunt receivedPurple Heart medals for their injuries.

The lawsuit was assigned to U.S. District Judge Edward Chen, an appointee of President Barack Obama.