The planned Purple Line route. (Maryland Transit Administration)

Maryland officials have asked a federal appeals court for an “emergency” order to suspend a lower-court ruling that has delayed construction on the Purple Line, saying the light-rail project faces a “crisis point.”

State officials need to “make a critical decision concerning the fate of the Purple Line on or about” Aug. 1, according to the court filing late Wednesday.

The lower-court judge, U.S. District Judge Richard J. Leon, has yet to rule on the state’s request that he reinstate the project’s environmental approval while the state appeals a ruling in a 2014 lawsuit seeking to block the project. Leon revoked that approval last August, which made the Purple Line ineligible for $900 million in federal grants. Construction, which was initially scheduled to begin last fall, also can’t start until a court reinstates the approval.

In a hearing June 15, Leon seemed to reject the state’s arguments, saying any delays stemmed from the state’s refusal to follow his order to scrutinize the project’s ridership estimates to account for Metro’s falling ridership. Any financial harm the state would incur due to legal delays, he said, would be “self-inflicted” because the state signed a $5.6 billion contract on the Purple Line while the lawsuit was pending.

Leon did not say during the hearing when he would issue a ruling.

In their latest filing to the U.S. Court of Appeals for the D.C. Circuit, Maryland officials said they were asking the appeals court to reinstate the environmental approval because Leon had “made it clear that will not rule promptly” on the issue.

If the environmental approval is not reinstated by Aug. 1, Maryland officials wrote, it “could cause the state to cancel the project, resulting in a financial loss to the state of approximately $800 million.”

The plaintiffs in the lawsuit — two Chevy Chase residents and a trail advocacy group — have said light-rail construction shouldn’t be allowed to start before the legal case is resolved because redoing the ridership projections might result in the state choosing a less expensive project with fewer environmental impacts.

Starting construction also would destroy 48 acres of forest and other wildlife habitat in Montgomery and Prince George’s counties, the plaintiffs have said.