President Barack Obama announced the White House is preparing an executive order offering transgender federal workers formal protection from discrimination at work, according to The Associated Press.

At least two other measures already prevent the federal government from firing people for being transgender, so Obama's announcement is largely symbolic, the AP reported. Still, advocates hailed the move as a powerful act of recognition for transgender Americans by the first American president to even utter the word "transgender" in a speech.

"The majority of Fortune 500 companies already have nondiscrimination policies to protect their employees because it's the right thing to do and because many say it helps to retain and attract the best talent. And I agree. So if Congress won't act, I will," Obama told a supportive crowd in the East Room of the White House during a reception marking Lesbian, Gay, Bisexual and Transgender Pride Month, according to the AP.

The Human Rights Campaign, the nation's largest LGBT rights group, praised Obama's announcement as a "crucial and historic measure," the AP reported.

"Each and every American worker should be judged based on the work they do, and never because of a fundamental aspect of who they are - like their gender identity," said HRC President Chad Griffin, according to the AP.

The White House declined to provide any details about the executive order that Obama has directed his staff to prepare for his signature, but LGBT rights groups said the order will likely mirror one that President Bill Clinton signed in 1998 that barred the federal government from firing workers for being gay and lesbian, the AP reported.

Activists said they expected Obama's executive order would include language specifically referring to gender identity, enshrining those protections in a more formal manner, according to the AP.

In the White House reception, Obama thanked activists for supporting and guiding his administration on same-sex issues and equality policies, the AP reported. He also cited influential figures in his own life, including an old college professor, who he said helped shape how he thinks about many of these issues.

He also repeated his call for Congress to act to ban discrimination for all workers based on gender identity and sexual orientation, according to the AP. "We've got a lot to be proud of, but obviously we can't grow complacent. We've got to defend the progress that we've made," he said.