Trump's decision, announced Wednesday on Twitter and sparking bipartisan outrage on Capitol Hill, comes after the White House was lobbied by conservatives on the issue, including Rep. Vicky Hartzler, who proposed an amendment on the defense authorization bill to ban the Pentagon from paying what Hartzler called "transition surgeries," as well as hormone therapy. The Missouri Republican lobbied the White House in recent weeks to do something on the issue, a GOP congressional aide familiar with the situation told CNN.
House Republican leaders knew the White House was already looking to change policy related to transgender people, but only as it relates to how or whether taxpayer money is being used for medical treatments, two Republican leadership sources told CNN.
Trump's announcement on a total ban of transgender people serving in the US military was "far beyond leaders' expectations and caught many by surprise," one of those sources told CNN.
Hartzler tried to engage with Defense Secretary James Mattis on service members' gender-related medical costs before the House took up the defense authorization bill, the aide said. When her amendment to that bill failed, she went to the White House to "address the issue" before the security spending bill was brought to the floor, a GOP congressional aide familiar with the situation told CNN.
While Hartzler was pushing for her proposal on the cost issue, she still supported
Trump's decision to ban transgender service members.
A study from the Rand Corporation
estimated the cost of medical services for transgender individuals in the military at $2.4 million and $8.4 million out of a $6.2 billion medical budget for the military.
CNN has reached out to the White House for comment on whether conservatives lobbied for the change and have not yet gotten a response. News of conservatives lobbying Trump on transgender issues was first reported by Politico.
Republicans on Capitol Hill are having difficulty responding because the Pentagon is still trying to explain the actual policy and how it would be implemented.
There were no plans to have another debate on the House floor on the taxpayer pricetag for gender-related medical expenses for members of the military. The House defeated Hartzler's amendment 209-214 on the defense authorization bill earlier this month, with 24 Republicans joining with Democrats to defeat the measure.
Aides stress that, among those who did not want the Pentagon to pay for these costs, there was concern about losing a second battle on the floor after Hartzler's amendment on the defense bill had been defeated.
Some conservatives, such as Rep. Mark Meadows and others in the Freedom Caucus, had been threatening to try to kill the spending package if the transgender health provision was not included, but Republican leadership was confident they had the votes to get the bill over the finish line, according to congressional aides.
House conservatives were trying to avoid a roll-call vote, too, pushing leadership to add the amendment banning medical expenses for trans service members as a "self-executing" provision to the House Rule for the security bill, which would have avoided a specific vote, according to a senior GOP aide. But leadership rejected that idea. On Wednesday afternoon the final parameters for debate on the spending bill were set and no amendments or changes to the bill were allowed ahead of floor votes on the military portions of that legislation.
Congressional aides said none of the defense committees -- House or Senate armed services and the defense appropriations panels -- were given any kind of notice or briefing on the decision.
House armed services committee Chairman Mac Thornberry told CNN Trump's decision appeared to catch the Pentagon by surprise, too, in addition to Congress.
"It was a complete surprise, not only to us but to the Pentagon apparently," Thornberry said.
Asked if he agreed or disagreed with Trump's decision, Thornberry said: "I don't know what it means."
Florida Rep. Tom Rooney, who served in the Army in the JAG Corps, admitted he didn't know what the administration policy announcement was because he missed the tweets.
He supported the effort to ban the Pentagon from using taxpayer money to cover medical costs of transgender medical procedures. But he told reporters the President's tweets on the new transgender policy "throws us off" the message about what the Republican Congress is accomplishing.
He pointed to the President tweeting about Attorney General Jeff Sessions when the Senate was making progress on repealing Obamacare, and the President tweeting last month about something off-topic on the same day that the House passed an immigration bill known as "Kate's Law" that the administration supported.
But things may be different in the Senate, where Sen. John McCain -- who criticized Trump's move Wednesday -- could soon be presiding over his defense policy bill when health care is done.
"I would assume there will be an effort on the floor to do something," Sen. Jack Reed, the top Democrat on the Armed Services panel, told CNN.