Washington (CNN) - U.S. Sen. Joe Lieberman introduced a bill Wednesday that would officially repeal the military's controversial "don't ask, don't tell" policy regarding gay and lesbian service members.
A separate repeal bill was previously introduced in the House of Representatives.
"To exclude one group of Americans from serving in the armed forces is contrary to our fundamental principles as outlined in the Declaration of Independence," Lieberman recently said in a written statement.
It "weakens our defenses by denying our military the service of a large group of Americans who can help our cause."
The legislative push comes in the midst of a Pentagon review on how to successfully implement a repeal of the policy, which was enacted under President Bill Clinton in 1993. Top Defense Department officials will testify before the House Armed Services Committee on Wednesday to discuss the review.
"Don't ask, don't tell" bars openly gay, lesbian and bisexual individuals from serving in the U.S. military, and prevents the military from asking a service member's sexual orientation. However, if the military finds out - from any source - that a service member is gay, the person can be discharged.
President Barack Obama and Joint Chiefs of Staff Chairman Adm. Mike Mullen support a repeal of the policy. Some senior members of the military, however, have expressed concern over the impact of a repeal of the ban on unit cohesion and morale, among other things.
Last month, Defense Secretary Robert Gates announced that the Pentagon had taken the first steps to prepare for a repeal of "don't ask, don't tell." Laying the groundwork for a repeal will take more than a year, he said. In the interim, he noted, the Defense Department will start enforcing the policy "in a fairer manner."
The defense secretary told members of the Armed Services Committee that "a guiding principle of our efforts will be to minimize disruption and polarization within the ranks, with special attention paid to those serving on the front lines."
Gates also said that the Pentagon will ask the RAND Corporation to update a study it conducted in 1993 on the impact of allowing homosexuals to serve openly in the military.
Since the "don't ask, don't tell" policy was implemented, more than 13,500 service members have been discharged, according to Rep. Jim Moran, D-Virginia. In 2009, there were 428 discharges under the policy - the lowest rate of discharge since implementation, he said. The highest year was 2001, with 1,227 discharges.
Sixty-nine percent of Americans believe openly gay people should be allowed to serve in the military, according to a February 12-15 CNN/Opinion Research Corp. poll. Twenty-seven percent are opposed to such a change.
In 1994, shortly after the "don't ask, don't tell" policy was implemented, 53 percent of Americans believed openly gay people should be allowed to serve in the military, while 41 percent were opposed.