Trenton, N.J. ? The biggest public works project in the U.S. — a $9 billion-plus train tunnel connecting New Jersey and New York City — is dead in its tracks.

New Jersey Gov. Chris Christie said Wednesday he is sticking by a decision announced earlier this month to kill the project because of runaway costs. He rejected a variety of financial proposals offered by the federal government to salvage the tunnel under the Hudson River, saying none of them fully relieved New Jersey of responsibility for overruns.

“It’s a dollars-and-cents issue. I cannot place upon the citizens of the state of New Jersey an open-ended letter of credit,” Christie said.

The decision to abandon construction more than a year after it began burnished the Republican governor’s reputation as a cost-cutter but was criticized as foolishly shortsighted by transportation advocates, train riders, union leaders and some Democrats. It also leaves New Jersey with nothing but a $600 million hole in the side of the hill.

Supporters of the project — an idea that has been on the drawing board for about 20 years — said it would create 6,000 construction jobs and thousands more jobs afterward, as well as ease train delays in a region with one of the nation’s longest commute times.

Currently, Amtrak and NJ Transit, the state’s commuter railroad, share a single, century-old tunnel underneath the river that has been at capacity for years. Just this week, a derailment outside New York’s Penn Station snarled the commute for tens of thousands of people.

U.S. Transportation Secretary Ray LaHood, who had implored Christie to reconsider, called the decision “a devastating blow to thousands of workers, millions of commuters and the state’s economic future.” He said commuters will see “no end to traffic congestion and ever-longer wait times on train platforms.”

Sen. Frank Lautenberg, a New Jersey Democrat who helped secure federal funding for the tunnel, said: “The governor has once again put politics over performance.”

Christie essentially had the last word on the project because it couldn’t go forward without New Jersey’s contribution. NJ Transit was running the project.