The Southwest light-rail line just got $81 million from Hennepin County to keep construction rolling while the project awaits word on nearly $1 billion in federal funding.

The $2 billion extension of the existing Green Line — the most expensive public works project in Minnesota history — will connect downtown Minneapolis to Eden Prairie. Passenger service is expected to begin in 2023.

On Thursday, the Hennepin County Board and its rail authority approved the project’s third “letter of no prejudice” — a commitment of local money in anticipation of a $929 million grant from the Federal Transit Administration.

This is the third such letter the project has received since 2018. Two previous funding extensions from local coffers totaled about $281 million. The letters are administrative actions to keep the project moving, officials said.

The Metropolitan Council, which will operate the 14.5-mile Southwest line, applied for a federal grant in August 2019 and expects it to be funded by June 30, said project spokesman Trevor Roy.

So far, $640 million in local and state money has been spent on construction of the line.