The reprieve for a major new commuter rail tunnel under the Hudson River, once set to be the largest public works project in the U.S., never arrived.

Proponents of the megaproject, estimated at $8.7 billion, failed to convince New Jersey Gov. Christopher Christie (R) that the state would not have to make up cost overruns that some claimed would boost the total price of the project to $13.7 billion.

“In the end, my decision is not changed,” Christie said. “I cannot place upon the citizens of the State of New Jersey an open-ended letter of credit.”

Christie emphasized his objection to paying for costs not covered by $6 billion in funds from the Federal Transit Administration and the Port Authority of New York and New Jersey.

“What the proponents of this plan are asking me to do, on behalf of citizens of this state, is to hand them over a blank check. I simply will not do that to the people of the State of New Jersey.”

Christie’s action brought swift and strong reactions from Transportation Secretary Ray LaHood and N.J. Sen, Frank Lautenberg, but the governor was unmoved. Click here for LaHood statement and here for Lautenberg reaction.

According to observers and published reports, Christie may seek to use New Jersey’s existing $2.7-billion project commitment to shore up its depleted transportation trust fund for bridge and highway repair. Not clear is how FTA will reassign its $3 billion earmark to other rail projects in the U.S., or how Port Authority will reallocate its share. Some pundits support that position.

This story was updated on Oct. 28, 2010.