Demonstrators gathered in Elm Street Park on Labor Day to protest the closing of the Georgetown Branch Trail on Sept. 5. (Jahi Chikwendiu/The Washington Post)

Purple Line opponents asked a federal judge Wednesday to prohibit a project contractor from cutting down trees along a Montgomery County trail while a lawsuit against the line's construction is pending.

It was the latest effort by opponents of the light-rail line to block it from being built.

During a hearing Wednesday, U.S. District Judge Richard J. Leon said he would hear more arguments Sept. 19 to decide whether to block Maryland's contractor from clearing trees along the three-mile Georgetown Branch Trail until the lawsuit is resolved. Leon said he also would rule as early as Friday on the opponents' request for a shorter-term restraining order that would prohibit tree clearing until he decides whether a longer-term ban for the duration of the lawsuit is warranted.

Leon indicated that he would rule on a longer-term ban by Sept. 25 and asked an attorney for the state why tree cutting couldn't be delayed until then.

"I don't think that's asking much on a project of this magnitude," Leon said, citing the $900 million in federal grants committed to the project's more than $2 billion construction costs.

Maryland officials have said that larger trees between downtown Bethesda and Silver Spring are scheduled to be cut down beginning the week of Sept. 18. The state's contractor closed the popular recreational trail Tuesday, saying it would remain off limits for four to five years while the 16-mile light-rail line's western segment is built in the corridor. Workers began cutting smaller trees — those less than nine inches in diameter — this week, an attorney for the state said.

In a recent court filing, the Purple Line opponents — two Chevy Chase residents and the advocacy group Friends of the Capital Crescent Trail — said cutting down trees before the lawsuit is resolved would cause "irreparable environmental damage."

"Once you cut down a tree, it can't be put back up," David Brown, the attorney for the opponents, told the judge.

Tyler Burgess, a U.S. Justice Department attorney, said the opponents' legal arguments hadn't cleared a "very high bar" for a temporary restraining order, which she deemed "very extraordinary relief."

Albert Ferlo, a lawyer who represents the Maryland Department of Transportation, told Leon that every day of construction delays costs the state up to $433,000 in potential contract penalties and other costs.

MDOT spokeswoman Erin Henson said after the hearing that the opponents were "abusing the judicial process" to fight the rail project.

"Their tactic is to delay, delay, delay in an effort to get us to abandon a critical project for the National Capital Region — something that will never happen," Henson said.

The state is appealing an unfavorable ruling in a 2014 lawsuit opposing the Purple Line, but an appellate court recently permitted construction to continue while a three-judge panel considers the case.

The state is under pressure to clear the heavily wooded trail before April, when it must abide by federal restrictions against cutting down trees during the bird nesting season.

The plaintiffs are renewing their arguments that the U.S. Transportation Department failed to require Maryland to show it can afford to maintain and operate the region's existing transportation system, particularly Metro, before using federal aid to expand it.

The plaintiffs also argue that the Purple Line shouldn't receive federal construction funding until it abides by Leon's previous order to redo the project's ridership forecasts to reflect Metro's declining ridership and safety problems.

The state has yet to redo that environmental analysis — a process that could take months — and is appealing Leon's order to a higher court.

The Purple Line will operate separately from Metro, but 27 percent of its riders are expected to come from people transferring to and from Metro.

State and federal officials have told Leon that they have already determined that Metro's declining ridership would have no significant effect on the Purple Line.