A group of 143 House lawmakers on Tuesday sent a letter to President Trump urging him to back off his plans to curb transgender military service.

The Democrat lawmakers, about one-third of the chamber, said there was no evidence for Trump's earlier claim that transgender troops are costly and disruptive, and that barring their service based on their sex is unconstitutional.

Trump on Friday formally ordered the Pentagon to abandon plans to recruit transgender troops and stop all funding of gender reassignment surgeries by March, a move the White House said was aimed at rolling back the open service instituted by the Obama administration.

"We urge you again to join us in honoring all those who protect our nation, to fully respect the rights of the citizens you serve, and reconsider the ill-advised and indefensible policy you have moved to implement," according to the group, which included Minority Whip Steny Hoyer, D-Md., Rep. Adam Smith, D-Wash., ranking Armed Services Committee member, and Rep. Tim Walz, D-Minn., the ranking Veterans Affairs member.

The letter also pointed to a previous study saying transgender-related medical costs would not be more than $8.4 million.

"This is less than one-hundredth of one percent of the military's nearly $50 billion health care budget," the lawmakers wrote. "Or, for comparison, roughly equal to the cost to taxpayers of four of your weekend trips to Mar-a-Lago resort."

Trump took many in the Pentagon and Capitol Hill by surprise when he announced via a series of tweets in July that transgender troops would no longer be allowed to serve in any capacity. The newly issued presidential memorandum tasks Defense Secretary Jim Mattis with deciding how to deal with currently serving transgender service members.