President Trump sang the National Anthem during an event at the White House on Tuesday. (Susan Walsh/AP)

President Trump is fighting a bipartisan plan to fund the much-touted expansion of veterans health care he signed into law on Wednesday, as the White House argues against a boost in federal spending to fund the new initiative.

“The VA Mission Act authorizes and expansion of veterans’ access to private health care, but the bill does not reserve federal money to pay for it. A group of powerful Senate committee chairmen from both parties aims to remedy that by advancing a separate measure for the new $50 billion law, saying this is the best way to ensure the new programs give veterans access to medical care.

But the White House has been lobbying Republicans to vote the plan down, instead asking Congress to pay for veterans programs by cutting spending elsewhere.

The opposition to the funding plan is the latest demonstration of Trump’s variable approach to the longtime stated Republican goal of fiscal discipline. On some issues, most prominently last year’s $1.5 trillion tax bill or immigration measures such as the border wall, Trump has signed off on legislation projected to massively increase the federal deficit.

On others, such as the veterans bill and emergency legislation to support communities impacted by last year’s devastating hurricanes and the California wildfires, he has demanded offseting spending cuts. Without passage of the veterans funding bill soon, lawmakers and veterans groups warn that the Veterans Affairs will be forced to make difficult trade-offs about which veterans programs should be funded.

“You shouldn’t have to ask Congress every year for money to take care of veterans,” said John Hoellwarth, communications director for AMVETS, one of the country’s major veterans groups.

The current debate could be a preview of spending fights to come, with the next government shutdown deadline looming on Sept. 30, just ahead of the November midterm elections. Trump has already issued demands for more money for his border wall, something likely to meet resistance in the Senate, setting up the possibility of a shutdown showdown weeks before elections that will decide control of Congress.

In a memo circulated privately to Republican senators this week, White House officials slammed the leading veterans funding proposal as “anathema to responsible spending” and that predicts it would lead to ballooning costs and “virtually unlimited increases” in veterans’ spending on private health care.

“Without subjecting the program to any budgetary constraint, there is no incentive to continue to serve veterans with innovative, streamlined and efficient quality of care,” the administration says in the memo, which was obtained by The Washington Post.

Sen. Richard C. Shelby (R-Ala.), head of the Senate Appropriations Committee, argued that if Congress does not ratify his proposal, the alternative could be to cut $10 billion a year for five years from existing programs, including initiatives within the Veterans Affairs Department.

“If we don’t get on it we’re going to have a hole of $10 billion in our approps,” Shelby said Tuesday, predicting “some real trouble.”

Shelby is joined in his effort by the top Appropriations Committee Democrat, Patrick J. Leahy (Vt.), as well as the leaders of the Veterans’ Affairs Committee, Chairman Johnny Isakson (R-Ga.) and Sen. Jon Tester (D-Mont.).

Their coalition reflects a renewed commitment in the Senate to completing spending bills on a bipartisan basis after years of budget dysfunction.

Their effort has run into stringent opposition from a White House still reeling from conservative backlash to the $1.3 trillion government-wide spending bill Trump signed in March. The deal broke through previous spending caps with huge increases in domestic spending Democrats demanded in exchange for military spending sought by Republicans.

Conservatives, including close Trump allies, publicly slammed the spending package and criticized Trump for signing it, and the administration has subsequently dug in against new spending and worked to claw existing spending back.

Trump frequently touts his support of veterans and members of the armed services, promising during the campaign to fix VA and give more veterans access to private health care. Aiming to keep those promises, veterans programs are one of the few areas aside from the military where Trump has encouraged new spending.

But the White House says it won’t accept new spending on the veterans bill above the overall domestic spending levels already negotiated with Congress, arguing enough money can be found to fund it within existing budget limits.

“The President’s 2019 Budget supports a new, consolidated community care program for veterans and all of VA health care within the discretionary caps already in place. We have a responsibility to provide our Veterans with the care they deserve, while also being good stewards of the taxpayer dollar,” the administration said in a statement.

The VA spending fight could come to a head as soon as this week, as lawmakers prepare to take up a military construction and VA appropriations bill that the bipartisan group of chairmen wants to use to fund the VA Mission Act’s program.

The tension over how to pay for the legislation is part of a larger debate over private care for veterans. The Mission Act revamps a private-care program Congress approved in 2014 after a scandal over fudged patient wait lists for medical appointments. The new, bipartisan measure consolidates numerous private-care programs that were fragmented and inefficient and drew support from disparate veterans groups that often disagree. It also expands stipends for a popular program that pays family caregivers of veterans who served in Vietnam and later wars, for example, a priority for advocates.

Funding questions dogged the bill during its debate in the House, where Democrats had sounded an alarm on what they called the legislation's unsustainable costs. Rep. Tim Walz (Minn.), the House Veterans' Affairs Committee's ranking Democrat, described a "stark picture of a VA forced to cannibalize itself in order to pay for private care," with potential funding cuts to investments in buildings,  direct patient care, suicide prevention, medical research and job training.

The legislation’s biggest costs, though, will come in new doctor’s appointments outside the VA system, which now sends roughly a third of veterans to private doctors. The Congressional Budget Office estimated the increase at 640,000 veterans each year, particularly with new authorization for VA to negotiate a contract for care at private walk-in clinics.

But the shift to greater outsourcing — arguably the top White House priority for veterans — has been controversial. It was a key reason the president fired VA Secretary David Shulkin in March after the White House suspected that he was not pushing “choice” aggressively enough. Many Democrats, traditional veterans service organizations and federal employee unions adamantly oppose the goal of giving veterans unfettered options to choose private doctors, arguing that such a change would starve VA’s vast system of government health care, the country’s largest.

Another sticking point is cost. There is no reliable estimate and little research to determine how much taxpayers pay for a private medical appointment versus one inside VA’s system of 1,300 clinics and hospitals. Conservatives and liberals agree that outsourcing tends to cost more because VA care has economies of scale, but how much more is a question that will affect the spending debate between the senators and the White House.

“The Congressional Budget Office has not done a good job projecting how much private care costs because VA doesn’t share its data and often doesn’t collect it, so you can’t make an accurate prediction,” acknowledged Dan Caldwell, executive director of Concerned Veterans for America, a White House-allied group backed by the conservative industrialists Charles and David Koch that has led the push for veterans to decide where to get their medical care and from whom.

Caldwell said, however, that the White House is right to oppose lifting the budget caps to cover the Mission Act. He said that consolidating the multiple private care programs that exist now should control the new bill’s costs.

“I think they can pay for this program without raising the caps,” Caldwell said.

Traditional veterans groups such as Hoellwarth’s AMVETS are suspicious of what they see as a White House strategy to privatize VA. Any they were adamant that if the spending caps aren’t raised, the agency could be forced to take money from other valuable veterans’ benefits to ensure that veterans have access to health care.

Phillip Carter, a senior researcher at the Rand Corp., a nonprofit think tank, said the bill creates another unanswered question on cost: It could push up the demand for medical care at VA hospitals as the pressure on them eases with more outside appointments.

“When the agency agrees to fund new programs as it has done here, there is potential for far more veterans to use the system, whether it’s inside VA or outside,” Carter said. “That’s what the White House and Congress have to reconcile themselves to, demand going up overall and costing more.”