WASHINGTON — When House lawmakers start debate on massive reforms to the veterans health care system this week, they won’t just be hearing from veterans pushing for changes.

A coalition of conservative groups typically not connected to Veterans Affairs issues sent a letter to House leaders on Monday pushing them to rein in department spending and shift more resources to private-sector medical appointments for veterans who want them.

“Americans who put their lives on the line for our country should have the freedom to choose to use their VA benefits in the private health care market,” the letter states.

The effort — led by Concerned Veterans for America, a conservative voice in the veterans community in recent years — includes Americans for Prosperity, Heritage Action for America, National Taxpayers Union, Tea Party Nation and 11 other groups with ties to Republican Party donors and small-government initiatives.

It comes one day before the House Veterans’ Affairs Committee is scheduled to start debate on its draft of an overhaul to the VA Choice program, created in 2014 as a way to allow more veterans to receive care outside department clinics in the wake of a wait times scandal that forced the resignation of several top officials.

The House panel is also expected to review the VA’s new Veterans Coordinated Access & Rewarding Experiences (Vets CARE) proposal, which would further ease rules concerning veterans seeking medical appointments outside the VA system at government expense.

Supporters of the idea — including VA Secretary David Shulkin — insist the department must drop current restrictions on allowing veterans to see private-sector physicians to provide the best, most convenient care to veterans.

But critics, including federal unions, have blasted the plan as the first step towards privatizing VA operations, since it would shift billions in taxpayer dollars into private physicians’ pockets to provide care which may already be available within VA.

Last week, American Federation of Government Employees National President David Cox Sr. called the plan “voucherizing veterans health care” and accused Republican backers of working to destroy VA in an effort to undermine government health care.

The entry of new non-veterans groups into the debate adds another angle to that debate.

Monday’s letter insists Congress must act “to ensure that veterans who depend on the VA for their health care can seek care in the private sector – especially considering so many of them are currently trapped in poor-quality VA facilities.”

It also calls for more transparency on VA health care costs and “protection for the nation’s taxpayers with cost controls for the department.”

In fiscal 2001, the VA budget totaled $45 billion. The president’s budget request for fiscal 2018 is four times that, topping $180 billion. Several veterans groups have argued that given the demands on department services in recent years, that figure should be even higher.

They’ve also argued against using VA funds to pay for outside medical care, unless equal money is given to bolster VA services.

But CVA Policy Director Dan Caldwell noted that financial growth has come at a time where the veterans population is declining.

“Congress must embrace reforms to the VA medical system to ensure veterans receive the best care available and that taxpayer dollars are not being wasted,” he said. “Ensuring funds are being spent efficiently will allow the VA to provide veterans with a higher level of care for years to come.”

Several of the 16 letter signers have close ties with the Koch brothers network of conservative activist organizations. Others include Taxpayers for Common Sense, Taxpayers Protection Alliance, Campaign For Liberty and the Center for Individual Freedom.

The House Veterans’ Affairs Committee is scheduled to meet at 10 a.m. Tuesday to discuss the potential health reforms.