A Silver Line Metro train pulls into the Ballston Metro station. (Pete Marovich/For The Washington Post)

Virginia House Republicans placed a roadblock in the path to creating a new Metro oversight body Thursday, but both GOP and Democratic leaders said there is plenty of time left in the legislative session to reverse the move.

A House Transportation subcommittee voted along party lines for an amendment that would require Metro to weaken union protections and fix its pension deficit before the Metro Safety Commission is formed.

If sustained, the amendment would derail a lengthy effort in Virginia, Maryland and the District — which must all approve identical legislation — to establish the federally mandated commission or risk losing millions of dollars in federal transit aid.

The D.C. Council has approved the legislation, and it’s expected to pass in Maryland this legislative session.

The amendment’s sponsor, Del. J. Randall Minchew (R-Loudoun), said the change is necessary to rein in Metro’s labor costs. Otherwise, he said, new investments ordered by the commission would add to Metro’s expenses and lead to a tax increase.

The amendment’s sponsor, Del. J. Randall Minchew (R-Loudoun), said the change is necessary to rein in Metro’s labor costs.

“The Metro Safety Commission is a good idea, but this is the harbinger of a tax increase, make no mistake about it,” Minchew said.

But Del. David J. Toscano (D-Charlottesville) called the amendment “a hand grenade being rolled into the middle of the room. It totally blows up a process that a lot of people worked on, at the very last minute.”

The three jurisdictions are facing a Feb. 9 deadline to create the new safety commission — a deadline they readily acknowledge they won’t meet. But they hope to stave off the potential loss of millions in federal funding by showing the Trump administration that they are making significant progress.

The commission is to assume oversight control from the Federal Transit Administration, which was given the responsibility over a year ago after federal officials determined that the former body responsible — the Tri-State Oversight Committee — was woefully inadequate.

Virginia Transportation Secretary Aubrey Layne said GOP lawmakers might just be trying to draw attention to their ideas about how to fix Metro. He expressed hope that the commission would eventually win approval without conditions as the bill works its way through the General Assembly.

“It’s a long process,” said Layne, who is part of the administration of Gov. Terry McAuliffe (D). “We have to see how much of this is political rhetoric and how much is their real stance.”

The subcommittee’s chairman, Del. Gregory D. Habeeb (R-Salem), also noted that the amendment came “very early in the process” — shortly before voting for it.

Minchew said later that he told Layne he “will work in good faith with him to see [the safety commission] created to commence needed safety work.”

But Minchew added that it would be “irresponsible” to create the body “knowing full well it will mandate additional capital investments in the Metro system and ignore the question as to where this money will come from.”

Minchew’s amendment says the safety commission will be formed only after changes are adopted, including a revision of the Metro compact to drop the requirement that labor disputes be settled by arbitration.

Critics of binding arbitration say the practice has inflated Metro’s labor costs. Without it, however, Metro’s unions would drop their no-strike pledge.

The amendment passed by voice vote in the subcommittee, where Republicans outnumber Democrats 5 to 2.

If the amendment is included in the final bill and signed by McAuliffe, it would effectively guarantee that the safety commission is delayed for months or, more likely, years.

Revising the Metro compact, which outlines how the agency is governed and financed, requires approval of the District, Maryland and Virginia. It must then be endorsed by Congress. It has already taken months of laborious effort for the three to agree on the text of the legislation to create the commission.

The three jurisdictions notified former U.S. transportation secretary Anthony Foxx that they would not meet next month’s deadline for creating the panel, and in doing so they risk losing 5 percent of their federal transit aid. It’s unclear whether secretary-designate Elaine Chao will enforce the penalty.

The commission will be empowered to adopt and enforce Metro safety rules, conduct inspections, order “corrective action plans,” impose fines for noncompliance, issue subpoenas and compel the agency to spend more money on safety-critical issues.

The need for the Virginia General Assembly to approve the safety body has given Republican critics of Metro an opportunity to push measures they have long advocated for the transit agency, such as weakening its unions.

“This is the chance to strike at this thing,” Del. Timothy D. Hugo (R-Fairfax) said. “If you don’t fix it, you’re going to be in a death spiral.”

In an unusual move at the subcommittee hearing, Minchew withdrew a bill he had filed that would have required Virginia to formally urge a rewrite of the Metro compact. Minchew said he did so because the General Assembly had previously approved similar legislation but he had been unaware of it.