The Pentagon plans to undertake a yearlong review of the military's "Don't Ask Don't Tell" policy.

Since Congress laid out the policy in 1993, gay and lesbian soldiers have been allowed to serve in the armed forces as long as they don't openly declare their sexuality. Now President Obama and some lawmakers want to lift that restriction.

Senators on the Armed Services Committee grilled two of the nation's top military leaders about it Tuesday.

"We have in place a policy which forces men and women to lie about who they are in order to defend their fellow citizens," Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, said in a candid statement.

"To me, personally, it comes down to integrity," Mullen added.

Defense Secretary Robert Gates took a different tone, pledging to undertake the review "with no preconceived views." He cautioned lawmakers not to turn this into a political issue.

"I ask that as this debate unfolds you keep the impact that it will have on our forces firmly in mind," Gates said. He noted that lifting the restriction would affect many other policies like how soldiers are housed or discharged.

Such a lengthy review would strain an already overstretched military, Sen. John McCain (R-Ariz.) said.

The committee's ranking Republican also noted that Congress already undertook an extensive review of the issue before implementing "Don't Ask Don't Tell" in 1993.

"What has changed since these findings were written?" McCain said. "Has this policy been ideal? No it has been not. But it has been effective."

Senators who support repealing the policy pointed out that some NATO allies let gays openly serve. Those troops have been serving alongside the U.S. military for years, they noted.

Committee Chairman Sen. Carl Levin (D-Mich.) added that thousands of linguists and troops of strategic importance have left the military because of the policy.

"The Army is not a democracy. It is a meritocracy where service depends not on who you are but how well you do your job," Levin added.

The discussion will continue when military officers appear before the committee on Feb. 11.

Ambreen Ali writes for Congress.org.