WASHINGTON (AP) — Major veterans' organizations are voicing concerns about a Senate GOP bill to repeal the nation's health care law, fearing the impact of rising insurance costs and worried the underfunded Department of Veterans Affairs won't be able to fill the coverage gap.

While there are more than 21 million veterans in the U.S., only about 8 million receive health care from the VA. The others rely on Medicaid, purchase insurance on state or federal exchanges, have employer-provided insurance or have no coverage at all.

In a letter Tuesday to senators, Paralyzed Veterans of America, one of the six biggest nonpartisan veterans' groups, criticized an "opaque and closed" legislative process and proposed cuts to Medicaid that could lead to hundreds of thousands of lower-income veterans losing their insurance.

It joins a Democratic-leaning group, VoteVets, in opposing the bill. VoteVets launched a six-figure ad campaign in two states, mostly to pressure moderate Sen. Dean Heller, R-Nev., who faces a tough 2018 re-election race. Heller, who indicated his opposition to the bill last Friday, says he's worried that too many people will lose coverage.

Two other major groups, Disabled American Veterans and AMVETS, also are expressing concern about the Senate legislation backed by President Donald Trump. They are worried the beleaguered VA — already facing an emergency $1 billion shortfall — won't have enough money to provide federally paid health care to more patients and say VA must be better funded.

The American Legion, Veterans of Foreign Wars and Vietnam Veterans of America have expressed broader concerns about VA underfunding but aren't taking a position on the Senate bill.

"What will become of these veterans as they face higher insurance costs?" Carl Blake, associate executive director of Paralyzed Veterans, wrote in a letter sent to all 100 senators. He pointed to more than 1.7 million veterans now on Medicaid — nearly 1 in 10 — as well as veterans ages 45 to 64 who have benefited from tax credits offered under the Affordable Care Act, or Obamacare.

He noted that the bill lacks explicit protections to ensure that millions of veterans who are eligible for VA care, but opt to use private insurance, still receive tax credits.

"Congress can no longer fake listening to these men and women; evidence of it is beginning to show in the increasingly marginal health, welfare and quality of life for far too many veterans," Blake said.

The Senate bill will fail if just three of the 52 Republican senators oppose it, dealing a major blow to Trump. A vote was planned this week, but then abruptly delayed Tuesday by GOP leaders until after the July 4 recess.

The bill would phase out extra federal money that the Affordable Care Act is providing to 31 states to expand Medicaid to additional low-income earners. According to a Congressional Budget Office analysis released Monday, coverage losses would especially affect people between ages 50 and 64, before they qualify for Medicare, and with incomes below 200 percent of poverty level, or around $30,300 for an individual.

VA Secretary David Shulkin has told Congress he expects many more veterans to turn to VA if the Senate legislation becomes law, in part because it would reduce projected spending on Medicaid by nearly $800 billion over 10 years. He has declined to estimate the number of veterans affected until the legislative process "runs its course." Veterans' groups believe the figure could be 400,000, based in part on projected growth of veterans.

The Urban Institute says the number of uninsured non-elderly veterans dropped by 40 percent between 2013 and 2015, citing the Medicaid expansion and availability of tax credits under the Affordable Care Act.

"We are a safety net organization, and we tend to have veterans without other health access come to the VA," Shulkin said.

Adrian Atizado, Disabled American Veterans' deputy national legislative director, says VA hasn't been able to show it can handle its current workload of patients, let alone take on new ones. Earlier this month, the VA announced an unexpected $1 billion shortfall in its Choice private-care program, telling Congress it may need an emergency infusion of funds or risk delays to veterans' care.

"We believe any additional demand on the system may aggravate the current fiscal constraints and affect the delivery of care to millions of veterans who use and rely on VA," Atizado said.

The views of veterans' groups have been of special interest to Trump, who touts their electoral strength and points to veterans' issues as a top priority of his administration. Because of their appeal to independent voters, Democrats have been trying to recruit at least two dozen military veterans to challenge Republican incumbents in a bid to gain majority House control in 2018.

___

Follow Hope Yen on Twitter at https://twitter.com/hopeyen1