The American Civil Liberties Union and two other groups that advocate on behalf of transgender service members filed federal lawsuits Monday against President Trump's order to curb most transgender military service, which the White House announced on Friday.

"BREAKING: We're taking @realDonaldTrump to court to challenge the unconstitutional transgender military ban," the ACLU tweeted Monday morning. Earlier on Monday, Lambda Legal and OutServe-Servicemembers Legal Defense Network filed lawsuit in a Washington state district court. The groups represent two transgender people who want to enlist in the military and an enlisted service member who wants to become a warrant officer.

BREAKING: We're taking @realDonaldTrump to court to challenge the unconstitutional transgender military ban. pic.twitter.com/udV6P1hIJh — ACLU (@ACLU) August 28, 2017

"We promised that we would sue if the president took this action. The law is on our side; justice is on our side," Peter Perkowski, legal director for OutServe-SLDN, said in a statement.

Five transgender service members are already suing Trump, Defense Secretary Jim Mattis, and other top military officials in a D.C. federal court, and the latest filing comes days after the president ordered the Pentagon to drop plans to recruit transgender troops, halt their medical treatment, and determine within six months whether those currently serving can remain in the military.

The legal team behind the first lawsuit, which was filed Aug. 9, expects to file a motion for a preliminary injunction this week which, if successful, could block the administration from moving forward with the ban while the case is being heard by the courts.

The White House guidance was called a "purge" by advocates and was aimed at rolling back a new personnel policy issued last summer by the Obama administration allowing open transgender service. But it also appeared to allow Mattis some leeway in deciding which currently serving transgender troops may be allowed to remain.

The Pentagon has until March to institute the Trump rules, which the president first announced in a series of tweets July 26.

The transgender plaintiffs in the newly filed Lambda Legal and OutServe-SLDN lawsuit are Ryan Karnoski, 22, a Seattle social worker who wants to enlist; Staff Sgt. Katie Schmid, 33, a soldier serving at Joint Base Lewis-McChord who applied to be an Army warrant officer; and Drew Layne, 17, of Corpus Christi, Texas, who wants to join the Air Force, according to the two advocacy groups.