LGBT advocates on Thursday responded to news that the White House is preparing to issue guidance to the Pentagon on implementing President Donald Trump's ban on transgender troops.

In a series of tweets last month, Trump called for completely barring transgender people serving in the military.

According to several reports, the White House has watered down its demands, focusing instead on barring transgender people from enlisting in the military and refusing to pay for transition-related medical care for transgender service members.

(Related: White House gives Pentagon six months to create Trump's ban on transgender troops.)

Two groups, the National Center for Lesbian Rights (NCLR) and GLBTQ Legal Advocates and Defenders (GLAD), have already filed a federal lawsuit challenging the ban. Two additional groups, OutServe-SLDN and Lambda Legal, have promised to do the same.

“The President's willingness to attack his own troops is unprecedented and poses a serious threat to our nation's longstanding commitment to honor those who serve and to prioritize military readiness over politics,” said NCLR Legal Director Shannon Minter in a statement. “This ban needlessly takes aim at our courageous transgender servicemembers. This is not who we want to become: a country so committed to baseless discrimination that we are willing to sacrifice even our national security.”

OutServe-SLDN Executive Director Matt Thorn called Trump's order a “purge” based on bigotry.

“It is inconceivable that a man with a demonstrated incompetence in managing the small staff of the White House should have any credibility when it comes to making sound personnel decisions that will affect a fighting force of more than 1.8 million men and women,” Thorn said in a statement.

“We recognize this purge for what it is – a discriminatory attack on the people who have volunteered their lives for the defense of the country. It is arbitrary and capricious, a callous and questionable exercise of constitutional authority which is beneath the dignity of a Commander-in-Chief.”