It's important to conduct a detailed review of the effects of repealing "don't ask, don't tell," says U. S. Adm. Mike Mullen, the Joint Chiefs of Staff chairman.

He would prefer Congress hold off on passage of repeal until completion of a Defense Department review of the policy change expected to be completed in December, Mullen further said.

Mullen said on "Fox News Sunday", "Ideally, I would like the legislation to wait until we've completed the review so we can look at how to implement it when the legislation goes."

The House of Representatives and a Senate committee approved legislation last week, including a provision to allow the repeal of the 17-year-old "don't ask, don't tell" policy.

Even after passage of legislation by Congress, the change wouldn't take effect until after the Defense Department review, Mullen said. The review is to scrutinize the potential effects of repeal on troop readiness, recruitment and retention.

He supports repeal of the ban on gays serving openly in the military but only after the "critically important" review, Mullen further said.

He further said, "We've worked hard so far in this review to understand what's going on with respect to our troops. And I don't control the legislative calendar. And the other thing is recognizing the votes that took place, I certainly understand that. But, I think it could be many months before the legislation actually was finally completed and it was passed." (With Inputs from Agencies)