Secretary of Defense Robert Gates is urging lawmakers not to repeal the military’s “don’t ask, don’t tell” policy until the Pentagon completes a review of it.

Congressional Democrats have been eyeing the upcoming Defense authorization measure as a vehicle to scrap the ban on gays serving openly in the military.

But in a Friday letter to House Armed Services Chairman Ike Skelton (D-Mo.), Gates recommended “in the strongest possible terms” that Congress allow the Pentagon “to conduct a thorough, objective, and systematic assessment of such a policy change; develop an attentive comprehensive implementation plan, and provide the President and the Congress with the results of this effort in order to ensure that this step is taken in the most informed and effective manner.”

The letter, co-signed by Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, came in response to a Wednesday missive from Skelton asking for guidance on the matter. Gates said he would “strongly oppose any legislation that seeks to change this policy prior to the completion of this vital assessment process. Further, I hope Congress will not do so, as it would send a very damaging message to our men and women in uniform that in essence their views, concerns, and perspectives do not matter on an issue with such a direct impact and consequence for them and their families.”

If Congress heeds Gates and Mullen, it would effectively delay action until after the November elections. The high-level Defense Department review announced in February is expected to take about a year.