Gay rights advocates are calling on President Obama to sign an executive order to coincide with repeal of “Don't Ask, Don't Tell” that would ban discrimination in the military based on sexual orientation and gender identity.

Congress approved in December and the president signed legislation that ends the military's 17-year-old ban on open gay and bisexual service.

But the policy won't end until 60 days after top Pentagon officials and the president agree that the military is ready for the change. The Pentagon has said it expects to lift the policy this year.

In a letter addressed to Obama, Servicemembers Legal Defense Network (SLDN), which lobbied for repeal of the law, urged the president to protect LGBT troops.

“We … call on you to show the leadership of President Truman did when he issued an Executive Order banning racial discrimination in the armed services and to issue an Executive Order prohibiting discrimination in the armed services based on sexual orientation and gender identity to be effective on the date of repeal of 'Don't Ask, Don't Tell,'” the letter, signed by SLDN Executive Director Aubrey Sarvis, says.

Sarvis added in a statement: “Signing legislation that allows for repeal of 'Don't Ask, Don't Tell' was a necessary first step, but it is not sufficient for ensuring equality in the military.”

Pentagon officials have said they expect to implement few policy changes to accommodate for the end of “Don't Ask, Don't Tell.”