A veterans' healthcare bill that passed the House unanimously on Wednesday may stall in the Senate amid fighting over an unrelated provision in the stopgap government funding bill and opposition from federal employees' unions.

The "Jeff Miller and Richard Blumenthal Veterans Health Care and Benefits Improvement Act" was the last piece of reform legislation spearheaded by retiring Rep. Jeff Miller, chairman of the House Veterans Affairs Committee. The bill contained dozens of provisions, including increased healthcare benefits for homeless veterans and an expansion of education benefits for military widows and widowers.

But one provision in particular drew the ire of federal employees' unions who felt the bill paved the way for "pay inequity" by changing the process by which the VA decides how much to pay its officials. That provision would end the VA's current practice of setting some salaries using peer-based panels to keep paychecks consistent with the market.

The VA itself supports the change and has previously argued that the panels waste time and delay the hiring process while delivering few benefits.

The American Federation of Government Employees issued a letter to senators on Wednesday urging them to block the veterans reform bill unless the paycheck provision was removed.

VA leaders have weathered fierce criticism in the past for handing out generous bonuses while blaming a lack of funding for its failures. In 2014, the year whistleblowers exposed a nationwide scheme to cover up delays in healthcare access, the VA gave out $142 million in employee bonuses.

VA Secretary Robert McDonald has defended bonuses and higher salaries for his employees in the past by arguing that pay restrictions make the agency less competitive in attracting talent.

That opposition would likely be a hurdle even if the Senate could get to the bill. But the Senate hasn't gotten to the legislation at all, even after Sen. Johnny Isakson, chairman of the Senate VA Committee, took to the Senate floor on Wednesday to urge his colleagues to pass the Miller-Blumenthal bill.

"This bill addresses homelessness. It addresses [veterans'] healthcare issues. It addresses [research on] the possible passage of exposure to toxic waste," Isakson said. "We're a team of Americans, not Republican Americans or Democratic Americans, but committed Americans that want to see to it that our veterans get what was promised to them."

By Friday morning, however, the bill's fate was uncertain because the Senate was still wrestling with a continuing spending resolution. Democratic Sens. Joe Manchin and Sherrod Brown have put a hold on that bill and others slated for unanimous consent as they push for a long-term fix for an expiring healthcare provision for miners.

A Senate VA Committee spokeswoman told the Washington Examiner that aides have been "appealing to those senators to make an exception" for the veterans' bill before time runs out on the 114th Congress. But so far, the bill remains stuck, and a spokesman for Manchin did not return a request for comment about whether he planned to allow the veterans' benefits legislation, which enjoys bipartisan support, to pass.

A spokesman for Majority Leader Mitch McConnell's office did not return a request for comment about whether he would seek an alternate route for passage of the bill.

Federal employees' unions have moved to block previous bills that would increase accountability at the VA, which is the second-largest agency by personnel and the fifth largest by budget.

The VA's annual budget has grown steadily under President Obama. Even so, VA hospitals are still plagued by long lines, subpar care and wasteful spending.

VA employees caught in misconduct that puts veterans at risk often goes unpunished, and officials have even been allowed to defraud the agency without consequences.

Miller, who served as one of the VA's sharpest critics in the wake of the 2014 wait time scandal, will retire from his seat this year.

President-elect Trump floated the Florida Republican as a potential VA secretary during a campaign event this summer, and the House VA Committee chairman is still a rumored contender for the job.