Washington (CNN) -- Gay and lesbian members of the military should think twice before participating in a Pentagon survey on the controversial "don't ask, don't tell" policy, according to a key advocacy group pushing to overturn the current law.
The Servicemembers Legal Defense Network -- an organization that supports gays and lesbians serving openly in the military -- issued a statement Thursday saying it cannot recommend that lesbian, gay, or bisexual service members fill out the Defense Department questionnaire.
"There is no guarantee of privacy and (the Pentagon) has not agreed to provide immunity to service members whose privacy may be inadvertently violated or who inadvertently outs himself or herself," said Aubrey Sarvis, the group's executive director. "If a service member still wishes to participate, he or she should only do so in a manner that does not reveal sexual orientation."
Asked for his reaction, Defense Secretary Robert Gates said he is "strongly" encouraging gays and lesbian service members to complete the survey. Gates insisted during a Pentagon news conference that the confidentiality of respondents will protected. The survey is being conducted "in a very professional way," he asserted.
The Pentagon on Wednesday began sending out survey, which contains more than 100 questions seeking service members' views on the impact of repealing the "don't ask, don't tell" restrictions.
An administration official confirmed to CNN that the survey is being sent to 200,000 active duty troops and 200,000 reserve troops. The official declined to be identified because the survey had not officially been made public.
The survey, which service members can expect to receive via e-mail, asks about such issues as how unit morale or readiness might be affected if a commander is believed to be gay or lesbian; the need to maintain personal standards of conduct; and how a repeal might affect willingness to serve in the military.
It also asks a number of questions aimed at identifying problems that could occur when troops live and work in close quarters in overseas war zones. For example, the questionnaire asks military members how they would react if they had to share a room, bathrooms, and open-bay showers in a war zone with other service members believed to be gay or lesbian.
There also are several questions about reactions to dealing with same-sex partners in social situations.
The Pentagon established a team to conduct the survey earlier this year. President Barack Obama, Gates, and Joint Chiefs of Staff Chairman Adm. Mike Mullen have all publicly backed a repeal of the current policy. Defense Department officials insist the survey is aimed at determining the impact of a repeal -- not whether a repeal should happen.
Several members of the Joint Chiefs of Staff have said they want to see the results of the survey before they offer their final advice on the impact of a repeal to Obama and Gates.
In May, the House of Representatives approved a plan that would repeal the "don't ask, don't tell" policy after the military's internal review is completed and Obama, Gates, and Mullen sign off on the policy change. The Senate, however, has not passed the measure yet.
According to a senior U.S. military official with direct knowledge of the review process, the military needs until the end of 2010 to figure out how to implement a repeal in terms of housing, medical and marriage benefits, as well as issues involving the reinstatement of gay soldiers previously discharged under the policy.
In addition to distributing the survey, the Pentagon has also been soliciting opinions in a number of private meetings with troops.
The results of the review will not be available until December, the official said.
CNN's Barbara Starr and Alan Silverleib contributed to this report