Maryland Gov. Larry Hogan, left, speaks alongside state transportation secretary Pete K. Rahn at a 2015 news conference announcing that the state plans to proceed with the light-rail Purple Line project. (AP Photo/Patrick Semansky)

Maryland Gov. Larry Hogan (R) has asked the state’s attorney general to seek a court order compelling a federal judge to decide a lawsuit blocking construction of the planned light-rail Purple Line.

In a letter Thursday, Hogan asked Attorney General Brian E. Frosh to file a petition for a “writ of mandamus” asking the U.S. Court of Appeals for the D.C. Circuit to require the judge to rule in a 2014 lawsuit opposing the Purple Line project on environmental grounds. Lawyers for state and federal transit agencies have asked U.S. District Judge Richard J. Leon to dismiss the lawsuit.

Hogan wrote that he and Maryland Transportation Secretary Pete K. Rahn “have both concluded that it is necessary, on behalf of the citizens of Maryland, to take action to force U.S. District Court Judge Richard Leon to make a decision in the Purple Line litigation pending before him.”

Raquel Coombs, spokeswoman for the attorney general’s office, said she couldn’t comment on whether the office plans to seek such a court order, saying only, “The governor is aware of the legal strategy on this issue.”

Maryland officials are seeking a decision in the case as soon as possible because the rail project can’t secure nearly $900 million in critical federal construction grants until a judge restores the project’s environmental approval.

Leon revoked that approval in August, after agreeing with the lawsuit’s plaintiffs that state and federal transit agencies hadn’t sufficiently considered what impact Metro’s declining ridership could have on  Purple Line ridership. Lawyers for state and federal transit agencies have asked Leon to restore that approval, saying in December that they’d already concluded Metro ridership would have no significant impact.

State officials have complained that Leon is jeopardizing the project by taking too long to decide the case. Frosh had previously asked the judge to issue a ruling by April 28, saying the court delays threaten the viability of the project’s long-term $5.6-billion public-private partnership.

The governor’s letter said the state “stands to lose several million dollars because of this delay,” though the state has previously said in court filings that every month of delay costs the state more than $13 million. Construction of the 16-mile line between Montgomery and Prince George’s counties is estimated to cost about $2 billion.

Transit advocates say federal funding for new construction remains at risk because President Trump has proposed limiting such aid to projects that, unlike the Purple Line, already have a funding commitment.